The fourth interim report by the Smithwick Tribunal has been published.

In his two-page letter to the Oireachtas, Judge Peter Smithwick said that he had a "lengthy engagement" with the PSNI, the Northern Ireland Office and the British Home Office to try and get more details of intelligence the PSNI had claiming garda colluision in a number of murders.

The Tribunal is investigating claims that a garda in Dundalk passed information to the IRA which allowed them ambush the two most senior RUC officers to die in the Troubles.

Chief Supt Harry Breen and Supt Bob Buchanan died minutes after leaving a meeting in Dundalk Garda Station in March 1989.

Judge Smithwick, in his latest report, said the UK authorities were not able to provide any further details than already given to the Tribunal.

"I reserve any further comment on this for inclusion in my final report," the Judge said.

The tribunal has had serious delays due to the ill-health of a key witness, former Det Sgt Owen Corrigan.

Judge Smithwick said once he has an update on Mr. Corrigan's condition he will fix dates for hearing his evidence.

After that there will be submission by some of the legal teams representing various groups at the Tribunal.

Judge Smithwick said that while he must await hearing all the evidence before drawing conclusion’s he is collating and reviewing the evidence that has been given so far.