Former Fianna Fáil senator Willie Farrell said Mr Tom Gilmartin told him he was facing unlawful demands for money in relation to his developments in the late 1980s.
Mr Farrell recalled Mr Gilmartin saying the people behind the demands "make the Mafia look like monks". However, he didn't recall the developer referring to a specific demand for £5 million in 1989.
He said he knew Mr Gilmartin from childhood days, when they were growing up in the same part of Co Sligo.
In 1988/89, when he was a senator, he met the developer three or four times.
Asked if Mr Gilmartin had referred to a meeting he had with government ministers in Leinster House in February 1989, Mr Farrell said he didn't recall this. At the time, his wife was dying and contact with Mr Gilmartin wasn't the first thing on his mind.
Having gained the impression that Mr Gilmartin's difficulties were with the planners, he recommended he go to see a Dublin councillor, Mr Seán Gilbride, who was also from Sligo. But he denied taking the developer to see Mr Gilbride.
He said he advised Mr Gilmartin to get planning permission for a smaller development, and then try to extend this. However, Mr Gilmartin said it had to be "all or nothing".
In June 1989, Mr Gilmartin gave him a donation of £10,000 for a charity project the politician was involved in, the witness revealed.
Having had an accident and lost his job as a result, Mr Farrell had become involved in highlighting the plight of the disabled. He drove a pony and trap from Bundoran to Ballsbridge and took a stall at the Dublin Horse Show. This venture raised £21,000 for a disability unit in Bundoran.
He met Mr Gilmartin at this time, and the developer handed him a cheque with the payee left blank and told him to "put that in your pocket". Mr Farrell, who gave the cheque to his local health board shortly after, was surprised at the size of the donation.
Mr Gilmartin was a "hardworking, honest man who came up the hard way," he said. He felt "hurt" that Mr Gilmartin's big project was not getting the attention it deserved.
According to Mr Farrell, county councillors never took money "in rural Ireland". That might have happened in Dublin but it never did in Sligo and Mayo.
If councillors were taking money he would never have been elected to the Senate, he said. While many of his rivals in standing for the Senate had big cars and large bank accounts, he had driven around the country in a Citroën Dyane successfully canvassing for votes.