The planning inquiry has been told that Mr Cosgrave a member of Dun Laoghaire-Rathdown Co Council was paid £10,000 by Mr Dunlop on behalf of two companies which owned a controversial site at Carrickmines, Co Dublin, over the past decade.
Mr Cosgrave is one of nine past and current councillors in Dublin who have all denied either seeking or receiving money from Mr Dunlop in return for their support on the development.
In detailing individual payments to councillors, Mr Dunlop said Mr Cosgrave has asked him for money in return for his support.
He had provided Mr Cosgrave a son and grandson of former Taoisigh with several political donations including £5,000 in cash for the 1992 general election.
Mr Dunlop said he handed over to the money to the politician in a large envelope at a funeral in a church on Newtownpark Avenue, Blackrock.
Mr Dunlop said part of a £5,000 payment he gave to the former Independent and one-time Labour councillor John O'Halloran was in relation to Carrickmines. He also gave the Clondalkin-based politician a £2,500 donation towards a 1996 by-election.
Mr Dunlop said the late north Dublin councillor Jack Larkin (FF) had also received other payments in addition to the £1,000 he was given for his support on the Paisley Park/Jackson Way lands.
He described another deceased politician, Cyril Gallagher (FF), as someone "who occasionally took an independent line" on developments in his home area of Swords. Because they enjoyed a good personal relationship, Mr Dunlop said he had no hesitation in giving Mr Gallagher £1,000 for a local election.
Mr Dunlop said the late Tom Hand (FG) had offered to vote and promote land rezoning motions in return for payments. He claimed the long-serving councillor had received substantial payments from him throughout the history of Dublin Co Council Development Plan during the 1990s.
The late Seán Gilbride (FF) told the tribunal in 2001 that he had received £2,000 from Mr Dunlop towards the 1991 local election. He said he had provided Mr Dunlop with a receipt for the money as requested.
Senator Don Lydon (FF) denied Mr Dunlop's allegation he had received a number of payments in relation to his support for rezoning motions relation to Paisley Park and Jackson Way.
However, he recalled receiving two political donations from the PR consultant, including a sum of either £420 or £430 for the 1999 local elections. He was also happy to confirm Mr Dunlop's recollection that he had been paid £1,000 towards the Dáil and Seanad elections in 1993.