The Garda investigation into the leaking of information relating to Northern Ireland from the Department of Foreign Affairs in advance of last year's presidential election has ceased, the Taoiseach told the House.

"As I understand it, there is no ongoing investigation. The gardai believed they had a case and the DPP did not uphold that. In the normal course, the DPP is independent, so the case falls."

He was replying to the Fine Gael spokesman on justice, Mr Jim Higgins, who asked if the Garda investigation into the matter was ongoing and if he was confident that the guilty person would be brought to trial.

Mr Higgins said in the wake of a breach of the Official Secrets Act, whereby sensitive information had been leaked to a Sunday newspaper prior to the presidential election, there had been the high-profile arrest of a special adviser and the person's subsequent release.

Within the past 10 days, the Attorney General and the DPP had decided that there was no evidence against the person. Mr Higgins said that last October the leak was a matter of major concern. "The matter is still unresolved. Somebody leaked the document in question."

He asked if the Taoiseach had sought a report on the matter from the Minister for Justice and the Garda Commissioner.

Mr Ahern said he had no role in the decisions taken by the DPP and it would be inappropriate for him to make any comment on them.

"I understand that the gardai made a comprehensive report to the DPP after their investigations, which they obviously thought would stand up. The DPP had decided not to proceed."

Earlier, Mr Ahern recalled that on foot of the leak, the Government had decided to establish an interdepartmental committee on the protection of classified official information. It had now reported and had approved the implementation of key measures.

These included the putting in place of arrangements for the storage within departments of documents returned voluntarily by former ministers and ministers of state.

Priority should be given to a comprehensive review and a thorough revision of the Official Secrets Act.

One classification of "top secret" should be applied for interdepartmental purposes to particularly sensitive documents which because of their nature or content should only receive very limited, if any, circulation.