The Mahon tribunal will tomorrow begin investigating claims by the lobbyist Frank Dunlop that he made payments to a number of councillors on the former Dublin county council in relation to a development on land near Dublin airport in the mid-1990s.
Mr Dunlop will give evidence as part of a new module of investigation to be carried out by the tribunal into lands at Cloghran in north Dublin.
Mr Dunlop alleges he made payments of £1,000 each to Fianna Fáil councillors GV Wright, the late Cyril Gallagher and Tony Fox in return for their support.
He also alleges he paid another Fianna Fáil councillor, Seán Gilbride, a composite sum of about £2,000 for his support for the Cloghran development and two other developments in north Dublin, at Drumnigh and Cargobridge.
Mr Gilbride was one of the signatories to the motion on Cloghran.
Among the witnesses to be called before the tribunal this week will be Labour leader Pat Rabbitte, who was council chairman in 1993.
It is expected that Mr Rabbitte will be questioned about whether he was canvassed by the owners of the Cloghran lands or by Aer Rianta, which was strongly opposed to the rezoning application.
Mr Dunlop says he was introduced to the owner of the Cloghran lands, John Butler of Scafform, by Tim Collins of Ambrose Kelly architects. Mr Collins, a land agent who is a long-time friend of Taoiseach Bertie Ahern, has featured in several previous modules in which Mr Dunlop has given evidence.
Some 21 witnesses, including Mr Butler, are being called to give evidence in the module, which is expected to last less than two weeks.
Next week the tribunal will recall Ciarán Haughey and John Barnicle of Celtic Helicopters as part of the final stage of its investigation into other lands near Dublin airport known as Cargobridge.
Mr Haughey and Mr Barnicle recently retracted evidence which they had previously given to the tribunal that they received only £10,000 each from the proceeds of the sale of their portion of the Cargobridge lands in the mid-1990s.