The participating parties of the International Communist Seminar did the same as “the econimists no longer dared openly to contest the need for a political party of the working class”. They tried to prevent that that party would get the characteristics of a “vanguard of the working class” (read here the formulation of the ICS)
Read he following text an see the similarities of economism with the opportunism developed by the ICS.(in their by all participating "communist" parties subscribed "General Conclusions")
“The “Economists” (....)... asserted that the general political struggle against tsardom was a matter for all classes, but primarily for the bourgeoisie, and that therefore it was of no serious interest to the working class, for the chief interest of the workers lay in the economic struggle against the employers for higher wages, better working conditions, etc. The primary and immediate aim of the Social-Democrats should therefore be not a political struggle against tsardom, and not the overthrow of tsardom, but the organization of the “economic struggle of the workers against the employers and the government.” By the economic struggle against the government they meant a struggle for better factory legislation. The “Economists” claimed that in this way it would be possible “to lend the economic struggle itself a political character.”
The “Economists” no longer dared openly to contest the need for a political party of the working class. But they considered that it should not be the guiding force of the working-class movement, that it should not interfere in the spontaneous movement of the working class, let alone direct it, but that it should follow in the wake of this movement, study it and draw lessons from it.
The “Economists” furthermore asserted that the role of the conscious element in the working-class movement, the organizing and directing role of Socialist consciousness and Socialist theory, was insignificant, or almost insignificant; that the Social-Democrats should not elevate the minds of the workers to the level of Socialist consciousness, but, on the contrary, should adjust themselves and descend to the level of the average, or even of the more backward sections of the working class, and that the Social-Democrats should not try to impart a Socialist consciousness to the working class, but should wait until the spontaneous movement of the working class arrived of itself at a Socialist consciousness. As regards Lenin’s plan for the organization of the Party, the “Economists” regarded it almost as an act of violence against the spontaneous movement.
In the columns of Iskra, and especially in his celebrated work What is To Be Done?, Lenin launched a vehement attack against this opportunist philosophy of the “Economists” and demolished it.
1) Lenin showed that to divert the working class from the general political struggle against tsardom and to confine its task to that of the economic struggle against the employers and the government, while leaving both employers and government intact, meant to condemn the workers to eternal slavery. The economic struggle of the workers against the employers and the government was a trade union struggle for better terms in the sale of their labour power to the capitalists. The workers, however, wanted to fight not only for better terms in the sale of their labour power to the capitalists, but also for the abolition of the capitalist system itself which condemned them to sell their labour power to the capitalists and to suffer exploitation. But the workers could not develop their struggle against capitalism, their struggle for Socialism to the full, as long as the path of the working-class movement was barred by tsardom, that watchdog of capitalism. It was therefore the immediate task of the Party and of the working class to remove tsardom from the path and thus clear the way to Socialism.
2) Lenin showed that to extol the spontaneous process in the working-class movement, to deny that the Party had a leading role to play, to reduce its role to that of a recorder of events, meant to preach khvostism (following in the tail), to preach the conversion of the Party into a tall-piece of the spontaneous process, into a passive force of the movement, capable only of contemplating the spontaneous process and allowing events to take their own course. To advocate this meant working for the destruction of the Party, that is, leaving the working class without a party—that is, leaving the working class unarmed. But to leave the working class unarmed when it was faced by such enemies as tsardom, which was armed to the teeth, and the bourgeoisie, which was organized on modern lines and had its own party to direct its struggle against the working class, meant to betray the working class.
3) Lenin showed that to bow in worship of the spontaneous workingclass movement and to belittle the importance of consciousness, of Socialist consciousness and Socialist theory, meant, in the first place, to insult the workers, who were drawn to consciousness as to light; in the second place, to lower the value of theory in the eyes of the Party, that is, to depreciate the instrument which helped the Party to understand the present and foresee the future; and, in the third place, it meant to sink completely and irrevocably into the bog of opportunism.
“Without a revolutionary theory,” Lenin said, “there can be no revolutionary movement. . . . The role of vanguard can be fulfilled only by a party that is guided by the most advanced theory.” (Lenin, Selected Works, Vol. II, pp. 47, 48.)
4) Lenin showed that the “Economists” were deceiving the working class when they asserted that a Socialist ideology could arise from the spontaneous movement of the working class, for in reality the Socialist ideology arises not from the spontaneous movement, but from science. By denying the necessity of imparting a Socialist consciousness to the working class, the “Economists” were clearing the way for bourgeois ideology, facilitating its introduction and dissemination among the working class, and, consequently, they were burying the idea of union between the working-class movement and Socialism, thus helping the bourgeoisie.
“All worship of the spontaneity of the labour movement,” Lenin said, “all belittling of the role of ‘the conscious element,’ of the role of the party of Social-Democracy, means, altogether irrespective of whether the belittler likes it or not, strengthening the influence of the bourgeois ideology among the workers.” ˜(Ibid., p. 61.)
“The only choice is: either the bourgeois or the Socialist ideology. There is no middle course. . . . Hence to belittle the Socialist ideology in any way, to turn away from it in the slightest degree means to strengthen the bourgeois ideology.” (Ibid., p. 62.)
5) Summing up all these mistakes of the “Economists,” Lenin came to the conclusion that they did not want a party of social revolution for the emancipation of the working class from capitalism, but a party of “social reform,” which presupposed the preservation of capitalist rule, and that, consequently, the “Economists” were reformists who were betraying the fundamental interests of the proletariat.
6) Lastly, Lenin showed that “Economism” was not an accidental phenomenon in Russia, but that the “Economists” were an instrument of bourgeois influence upon the working class, that they had allies in the West-European Social-Democratic parties in the person of the revisionists, the followers of the opportunist Bernstein. The opportunist trend in Social-Democratic parties was gaining strength in Western Europe; on the plea of “freedom to criticize” Marx, it demanded a “revision” of the Marxist doctrine (hence the term “revisionism”); it demanded renunciation of the revolution, of Socialism and of the dictatorship of the proletariat. Lenin showed that the Russian “Economists” were pursuing a similar policy of renunciation of the revolutionary struggle, of Socialism and of the dictatorship of the proletariat.
Such were the main theoretical principles expounded by Lenin in What is To Be Done?
As a result of the wide circulation of this book, by the time of the Second Congress of the Russian Social-Democratic Party, that is, within a year after its publication (it appeared in March 1902), nothing but a distasteful memory remained of the ideological stand of “Economism,” and to be called an “Economist” was regarded by the majority of the members of the Party as an insult.
It was a complete ideological defeat for “Economism,” for the ideology of opportunism, khvostism and spontaneity.
But this does not exhaust the significance of Lenin’s What is To Be Done?
The historic significance of this celebrated book lies in the fact that in it Lenin:
1) For the first time in the history of Marxist thought, laid bare the ideological roots of opportunism, showing that they principally consisted in worshipping the spontaneous working-class movement and belittling the role of Socialist consciousness in the working-class movement;
2) Brought out the great importance of theory, of consciousness, and of the Party as a revolutionizing and guiding force of the spontaneous working-class movement;
3) Brilliantly substantiated the fundamental Marxist thesis that a Marxist party is a union of the working-class movement with Socialism;
4) Gave a brilliant exposition of the ideological foundations of a Marxist party.
The theoretical theses expounded in What is To Be Done? Later became the foundation of the ideology of the Bolshevik Party. Possessing such a wealth of theory, Iskra was able to, and actually did, develop an extensive campaign for Lenin’s plan for the building of the Party, for mustering its forces, for calling the Second Party Congress, for revolutionary Social-Democracy, and against the “Economists,” revisionists, and opportunists of all kinds.
One of the most important things that Iskra did was to draft a program for the Party. The program of a workers’ party, as we know, is a brief, scientifically formulated statement of the aims and objects of the struggle of the working class. The program defines both the ultimate goal of the revolutionary movement of the proletariat, and the demands for which the party fights while on the way to the achievement of the ultimate goal. The drafting of a program was therefore a matter of prime importance.
During the drafting of the program serious differences arose on the editorial board of Iskra between Lenin, on the one hand, and Plekhanov and other members of the board, on the other. These differences and disputes almost led to a complete rupture between Lenin and Plekhanov. But matters did not come to a head at that time. Lenin secured the inclusion in the draft program of a most important clause on the dictatorship of the proletariat and of a clear statement on the leading role of the working class in the revolution.
It was Lenin, too, who drew up the whole agrarian section of the program. Already at that time Lenin was in favour of the nationalization of the land, but he considered it necessary in the first stage of the struggle to put forward the demand for the return to the peasants of the otrezki, that is, those portions of the land which had been cut off the peasants’ land by the landlords at the time of “emancipation” of the peasants. Plekhanov was opposed to the demand for the nationalization of the land.The disputes between Lenin and Plekhanov over the Party program to some extent determined the future differences between the Bolsheviks and the Mensheviks.”
You can compare the formulation of "what is a communist pary" (here) with the Bolchevic formulation (here)
 Out “HISTORY OF THE COMMUNIST PARTY OF THE SOVIET UNION (Bolsheviks) - E D I T ED B Y A C O M M I S S I O N O F T H E C E N T R A L C O M M I T T E E O F T H E C. P. S. U. (B.) A U T H O R I Z E D B Y T H E C E N T R A L C O M M I T T E E of the C.P.C.U.(B), I N T E R N A T I O N A L P U B L I S H E R S , N E W Y O R K, Copyright, I 9 3 9, by INTERNATIONAL PUBLISHERS CO., INC, “Chapter Two. FORMATION OF THE RUSSIAN SOCIAL-DEMOCRATIC LABOUR PARTY. APPEARANCE OF THE BOLSHEVIK AND THE MENSHEVIK GROUPS WITHIN THE PARTY ( 1 9 0 1 - 1 9 0 4 )”, From Marx to Mao ML © Digital Reprints 2006