It was a "normal but not universal" practice for ministers to take papers from their private offices when leaving government, Dr Garret FitzGerald said yesterday.
"Some ministers take a considerable volume of their papers, others take none because they have no interest in them. It has worked well until now. There has never been, as far as I am aware, a case of documents being released which would be damaging to the national interest," he added.
Dr FitzGerald, who was minister for foreign affairs in the 1970s and Taoiseach twice in the 1980s, told The Irish Times that he had taken 400 boxes of papers relating to his periods in office.
These included copies of the weekly "green books" compiled by the Anglo-Irish division of the Department of Foreign Affairs at the time.
It was documents in these books, relating to the last government, which were used to suggest that Prof Mary McAleese sympathised with Sinn Fein.
Dr FitzGerald said he had given his papers to the UCD archives and that they were not available to anybody without his authority.
There was a question of discretion for outgoing ministers taking their personal papers, said Dr FitzGerald.
"There is an assumption that they will keep them safe and will not use them against the incoming government and in a manner damaging to the State," he added. "Some of what is contained in the papers would never be revealed, particularly relating to Northern Ireland."
Dr FitzGerald said a minister's private office was a separate institution within the Department, and had its own filing system. "Some ministers, like those in Foreign Affairs, would have copies of security documents, so it is obvious that anything taken from the Department should be kept secure."
At the weekend the former junior minister for foreign affairs, Mr Gay Mitchell, confirmed that a considerable number of the green books central to the Garda investigation into leaks of Government documents were among the private papers he had taken in 40 small boxes when he left office in June.
The documents relating to Northern Ireland had been untouched since, were kept under lock and key and could not have been leaked to the media, he said.
None of the politicians who had access to the leaked documents has yet been spoken to by gardai, although some journalists and department officials have.
The Taoiseach, Mr Ahern, told the Dail last week he was sure that gardai would be interviewing many members of the House. "They might be interviewing myself," he added.
