DUBLIN The Irish government on Thursday released an official report on allegations of "dirty tricks" surrounding a 1970 trial on arms supplies to Catholic Republicans in Northern Ireland, but the document failed to throw conclusive light on the murky affair.

The events of the so-called "arms trial" scandal -- involving a consignment of arms for Republicans who at the time were under siege in their communities in strife-torn Northern Ireland -- rocked the country.

At the start of the Northern Ireland troubles, then prime minister Jack Lynch sensationally fired two of his most senior ministers, Charles Haughey and Neil Blaney, and they were subsequently charged with conspiracy to import arms.

Lynch also fired another minister and a fourth resigned in sympathy.

Also charged were a Belfast Republican, an Army intelligence officer, and Irish-based Belgian businessman.

All were subsequently acquitted, and Haughey was later to serve as prime minister himself.

However the political convulsions led to the reshaping of the Irish Republic's policy on Northern Ireland and had huge ramifications for politics in the country for decades afterward.

Allegations that a key witness statement was tampered with emerged in media reports earlier this year after documentation for the trial was released by the country's national archives office under a 30-year rule.

A copy of a witness statement for the trial of the former head of military intelligence, the late colonel Michael Hefferon, appeared to have been tampered with.

In all, there were 16 deletions that appeared to have been made to protect the then defense minister, Jim Gibbons, and his assertion that he did not sanction the arms imports.

Gibbons' evidence was central to the state case against his ministerial colleagues.

The doctoring of the statement goes to the heart of the long-running controversy surrounding the events, and the question of whether the attempt to run guns to Northern Ireland was made with the knowledge and approval of the lynch government.

The new investigation for Justice Minister John O'donoghue fails to solve the mystery, and the probe was hampered by the fact that most of the key figures involved are now dead.

O'donoghue said that while the possibility of an attempt to suppress evidence cannot be ruled out definitively, it seems reasonable to infer that the likelihood of it "is remote."

Attorney General Micheal McDowell, in his report on the matter to O'donoghue, said that an official public inquiry at this stage "would serve no useful purpose," AFP reported.