Sir Jeffrey Donaldson was speaking after declassified Irish state papers revealed that a document about Sir Nicholas Fenn during his boating trip to Co Kerry was deliberately leaked by gardai and ended up with the IRA.

The DUP MP said he had never heard of the serious security leak until it became public knowledge thanks to declassified Irish state papers this week.

Sir Jeffrey said: “This deliberate leak of sensitive security information concerning the movements of the British Ambassador confirms once again that there were elements of the Garda who colluded with the IRA. This was indeed a serious leak of information when one considers that the IRA had murdered a previous British Ambassador in Dublin.

Sign up to our daily newsletter The i newsletter cut through the noise Sign up Thanks for signing up! Sorry, there seem to be some issues. Please try again later. Submitting...

“Yet, the Irish Government has completely failed to acknowledge this collusion let alone investigate it. There were key findings from the Smithwick Inquiry that pointed to collusion between Garda and the IRA that resulted in the brutal murder of two senior RUC Officers and yet there has been no indication that the Irish Government have followed up on this report and interviewed suspects.

“Despite their own failings, the Irish Government continues to be vocal in demanding that the UK authorities investigate every claim of alleged collusion in Northern Ireland. These double standards are unacceptable and we will not agree to a legacy process that does not include clear agreement on the actions to be taken by the Irish authorities to investigate crimes committed on their territory during the troubles, not least in relation to alleged collusion between members of the Garda and the IRA.”

However, the disclosure of Sir Nicholas’ protection details during his boating trip to Sneem in Co Kerry, was “not politically motivated”, the papers also claimed.

The British ambassador to Ireland also queried whether Irish officials had described his excursion as “irresponsible”.

Eamon O’Tuathail, the assistant secretary of the Anglo-Irish Section at the Department of Foreign Affairs, was told that Sir Robert Andrew, from the Northern Ireland Office, was seeking to discourage wedges being driven between the RUC and An Garda Siochana as a result of the incident.

In a confidential note uncovered by the Press Association, an Irish government official also stated that he believed Mr Fenn should have been forbidden from what he described as a “typically troublesome and self-indulgent excursion”.

The official complained that the Department of Foreign Affairs was not informed about the trip.

In a separate note, Department of Foreign Affairs official Declan O’Donovan told British charge Robert Stimpson that the unauthorised disclosure was a deliberate one at low Garda level.

“It was not believed at this point that the document had passed to or through the hands of a subversive organisation as had been alleged,” Mr O’Donovan added.

In a letter marked “secret”, Mr O’Tuathail wrote to Michael Lillis at the Anglo-Irish Secretariat in Belfast, stating that the protection of the British Ambassador has nothing to do with the Secretariat or the Northern Ireland Office.

“As so far as advising the Ambassador not to undertake any particular trip is concerned, we rely and must rely on the security assessment of the Garda Siochana,” Mr O’Tuathail added.

“Needless to say, a decision to make such a request to the Ambassador carries its own implications about the capacity of the State to protect the Ambassador in the exercise of his normal functions and therefore needs to be considered with particular care.”

“I would add that it does not seem to me that “forbidding” the British Ambassador to undertake a visit to any of the jurisdiction is language appropriate to the diplomatic relations of two friendly, democratic States.”

During a later meeting between Mr Fenn and Mr O’Tuathail, the Irish official said that no one had used the words “irresponsible” over his boating activities.