It came after former Workers' Party general secretary Sean Garland admitted that the party had employed "legal and illegal means" of fundraising.
The admission was contained in a letter to the East Berlin communist authorities, sent in February 1989. At the time, Mr Rabbitte and Tanaiste Eamon Gilmore were Workers' Party councillors, and went on to get elected to the Dail in the general election in June 1989.
Both of them said they were not aware of the letter sent by Mr Garland earlier that year to the East German authorities. They also said they were not aware of any illegal fundraising by the Workers' Party.
The discovery of the letter has revived questions about the Workers' Party's links at that time to the Official IRA, which was known for its involvement in bank robberies, punishment beatings and racketeering.
Mr Gilmore and Mr Rabbitte both said that they had raised their own funds for the 1989 general election campaign and had not received any funding from Workers' Party headquarters. This was backed up yesterday by Mr Garland himself.