Former Fine Gael TD Liam Cosgrave is the first of six councillors expected to be called as witness before the tribunal over the next fortnight.
Other high profile politicians accused of taking bribes include Fianna Fáil senator Don Lydon, former chairperson of Dun Laoghaire-Rathdown County Council Tony Fox and Independent councillor Colm McGrath, who is widely believed to be the politician famously described by Mr Dunlop as "Mr Insatiable".
They will be asked to explain allegations that they actively sought money from Mr Dunlop in return for their votes to rezone lands at Carrickmines in south Dublin on a number of occasions during the 1990s.
Mr Dunlop has claimed he made payments on behalf of landowners ranging from £1,000 to £5,000 for their assistance in attempts to get the land rezoned.
All are expected to repeat earlier written denials that they ever sought bribes and stress that any payments they ever received were legitimate political donations.
Several councillors including Mr Cosgrave and Senator Lydon have claimed they have no recollection of various meetings which Mr Dunlop has recalled in great detail.
Disgraced former TD Liam Lawlor is also due to appear before the tribunal to explain allegations he played a major role in advising the landowners how to make planning applications.
The tribunal has already heard evidence that the Isle of Man-based businessman Jim Kennedy and solicitor John Caldwell were the beneficial owners of two offshore companies Paisley Park Investments and Jackson Way Properties in whose name the land has been registered at various times.
Three of the people - Jack Larkin (FF), Cyril Gallagher (FF) and Tom Hand (FG) against whom Mr Dunlop has made allegations of corruption - are now dead.
Mr Dunlop has already admitted to the inquiry that he had actively and willingly participated in planning corruption. He has also confessed to committing perjury by misleading the tribunal during his first appearance at Dublin Castle in April 2000.
The former Government press secretary claims he paid out a total of £15,000 to councillors on behalf of Paisley Park in 1992, including payments of £3,000 each to Senator Lydon and Mr Hand who signed an unsuccessful motion to have the lands rezoned. He also told the tribunal he paid out £5,000 each to Mr Cosgrave and Mr Fox as signatories of a rezoning motion on the same lands that was passed in 1997.
In addition, Mr Dunlop claims he gave the former Independent councillor John O'Halloran a series of small payments totalling £5,000 for his general, pro-development support.
Since Mr Dunlop completed his testimony earlier this month, the tribunal has been hearing detailedevidence from a number of planning professionals and council officials who dealt with applications to rezone the lands at Carrickmines. However, the hearings have failed to shed any further light to confirm or deny the central thrust of Mr Dunlop's allegations.