MR De Rossa told the court the Official IRA no longer existed after it declared a ceasefire in 1972 as far as he was concerned.
He was speaking on the fourth day of his libel action against Independent Newspapers.
Mr MacEntee: "So you are saying in sworn evidence that the Official IRA ceased to exist in 1972?"
Mr De Rossa: "I am only telling you what I believed to be the case. I cannot tell you as a fact that the Official IRA ceased to exist. I do not know because I had no connection with it."
He told the court that social clubs in Belfast were frequented by members of the Workers Party. People in Belfast had to drink with others of like mind, otherwise they ran the risk of being beaten assaulted or even killed, he added.
Mr MacEntee asked whether he was referring to "Provie clubs and stickie clubs". Mr De Rossa said he was and added that following the split in the Republican movement there had been tension between those opposing violence and those promoting it:
The only clubs he had been in which were associated with the Workers Party were in The Markets and near the Springfield Road. There was no legal connection between the clubs and the party. Asked if the Workers Party derived any income from these clubs, Mr De Rossa said he was not aware but he had read press reports suggesting that money was transferred to the party. He suspected these donations would have been made to the party organisation in the North but there was never any record of such donations in his time on the ard comhairle.
Pressed on whether he had investigated reports of such donations, he said there would have been no reason to do so.
Asked about loans, Mr De Rossa said he had guaranteed loans for the party in the late 1980s. He readily agreed to go guarantor for a loan with the AIB and also with Lombard & Ulster. When he left the Workers Party, institutions pursued him and other members who had also guaranteed loans.
Later, under cross examination, Mr De Rossa said he was aware of only two Workers Party advice centres in Belfast. One was a £200 caravan which Councillor Seamus Lynch towed from housing estate to estate and the other was the party's office on the Springfield Road.
It was also possible that public representatives or aspiring politicians used social clubs as advice centres. And he was aware that there were councillors in Enniskillen, Dungannon and Downpatrick who might have had advice centres. Questioned about the cost of running these offices Mr De Rossa said there was no telephone in the caravan.
When Mr MacEntee asked him, whether he had signed cheques on behalf of the Workers Party, Mr De Rossa said he had not.
Mr MacEntee: "Never?"
Mr De Rossa: "I signed cheques when I was a member of the European Parliament drawn on an account I opened in favour of the Workers Party."
He was pressed on who signed the party cheques and said he guessed it was the general secretary and the treasurer. They would have been authorised by the ard comhairle of the party.
Mr De Rossa said he assumed that Mr Padraic Mannion as treasurer would have been one of the signatories as well as Mr Sean Garland as general secretary. Mr Garland had been general secretary of Official Sinn Fein, Sinn Fein the Workers' Party and the Workers' Party "as long as I can remember", said Mr De Rossa. When Mr Garland resigned as general secretary in 1991 he became party treasurer and would have continued to sign cheques.