The Northern Secretary, Mr Paul Murphy, and two of his predecessors have been asked to appear before an Oireachtas sub-committee which plans hearings into the Dublin and Monaghan bombings of 1974.
Mr Murphy, Dr John Reid and Mr Peter Mandelson are among several figures who have been asked to assist the sub-committee in its consideration of the Barron report into the bombings which killed 33 people.
The development is believed to mark the first time that any sitting or former member of the British government has been asked to appear before an Oireachtas committee.
It is also understood a senior officer in the Police Service of Northern Ireland (PSNI) has also been asked to appear.
The Taoiseach, Mr Ahern, said at a meeting yesterday with his British counterpart, Mr Tony Blair, that it would be appreciated if British officials asked to co-operate would do so.
Four former Ministers from the Fine Gael-Labour coalition in 1974 have also been asked to appear before the sub-committee of the Joint Oireachtas Committee on Justice, Equality, Defence and Women's Rights.
Dr Garret FitzGerald, Dr Conor Cruise O'Brien and Mr Paddy Cooney have each expressed major reservations about the report by former Supreme Court judge Mr Justice Barron. Their former cabinet colleague, Mr Justin Keating, has said the report is "splendid".
The sub-committee will start its work this morning when it hears from the families of those killed in the attacks on May 17th, 1974. In the course of hearings over the next five weeks, it will also hear from Mr Justice Barron.
Chaired by Fianna Fáil TD, Mr Sean Ardagh, the sub-committee will consider whether there should be a public inquiry into the bombings in the light of the judge's report.
The committee expects to hear next week from the former Ministers. It has asked to hear from Mr Murphy and his predecessors on February 10th and February 11th.