Fianna Fáil is examining details of a land purchase made jointly by its Meath by-election candidate, Cllr Tommy Reilly, and Mr Frank Dunlop in 1997, before deciding whether its national executive will formally ratify Mr Reilly to run.
He was selected at a convention before Christmas.
Party sources said yesterday that a decision on ratification would now come only after party officers had examined all aspects of the land deal and were satisfied that all was in order.
There is unease in some sections of the party in Meath and at some more senior levels of Fianna Fáil about the matter, although no allegation of wrongdoing or impropriety has emerged.
Senior party figures are concerned that any past business association between Mr Dunlop - who has said he bribed many Dublin councillors in the past - and their candidate may be electorally damaging, even if all aspects of the deal accorded with the highest standards.
Mr Reilly told The Irish Times last night that "everything was legal and above board" in relation to the purchase by him, in partnership with Mr Dunlop, of around 10 acres in the townland of Edoxtown near Skryne, Co Meath.
He had not put together all of the details yet, but had asked his solicitor to give Fianna Fáil all the information it required.
A Fianna Fáil spokeswoman said yesterday that the party had learned last Friday "that a number of questions had been put to Tommy Reilly by the local media regarding certain issues relating to property.
"As soon as the party became aware of this, contact was made with Mr Reilly, and a meeting was sought with the candidate.
"This meeting took place on Saturday, and there were discussions relating to the issues concerned.
"Following that meeting, further questions are now being put to the candidate, and the party will be seeking comprehensive answers as part of their inquiries into the matter."
Mr Dunlop confirmed yesterday that he and Mr Reilly, who had known each other for 25 to 30 years, had jointly purchased between 10 and 11 acres of land.
He believed they had done this in 1997 for £90,000 to £100,000 through a company used specifically for the purpose of buying that piece of land.
That company was registered with the Companies Registration Office, and everything was declared to the Revenue Commissioners, he said.
"We did not have any great intentions for it", said Mr Dunlop yesterday. "It is not near where you would be expecting any development to be taking place."
He said both he and Mr Reilly had thought that it might be possible at some point to build a house or houses on the land for family purposes - for a son or daughter. They had never considered making any attempt to have it rezoned or developed.
Mr Dunlop said the land, in the townland of Edoxtown near Skryne, "just sat there" for several years, with the two making no attempt to do anything with it.
At some point Mr Reilly gave just over one acre to his daughter, who applied for planning permission to build a house at one end of the land.
Mr Reilly bought out Mr Dunlop's half of the land in 2002 or 2003 for the same price he had paid for it. Mr Dunlop said he could not recall whether the planning permission application had been made at that point. Mr Reilly's daughter was granted planning permission for a house late last year after two appeals to An Bord Pleanaála.