The family of murdered prison officer Brian Stack says significant information was withheld by a section of the Gardaí investigating his killing.

It's claimed the information, which had come from an IRA informant and contained details of those responsible, had been on a file in Garda H.Q. since 1990.

Mr Stack's son, Austin, wants the Taoiseach to demand answers from the Garda Commissioner.

He's also looking for full access to all files.

Brian Stack was shot in Dublin in March 1983 and died 18 months later.