Army files being stored in England must be sifted through for clues to establish the extent of collusion in Northern Ireland during the Troubles, a senior politician has said.
The Assembly member is also calling for those involved in the Greysteel and Castlerock killings to come forward and account for their actions.
This Wednesday marks the 20th anniversary of the Greysteel massacre at the Rising Sun bar in the Co Londonderry village, in which six Catholics and two Protestants were shot dead by the UDA.
In an interview with the Belfast Telegraph last week killer Torrens Knight apologised for his role in the atrocity.
Mr Dallat has branded this "too little too late" and says if Knight is sincerely sorry he should expose any role north Antrim man Billy 'The Mexican' McFarlane – who was named in court documents and police statements – had in Greysteel.
Mr McFarlane was questioned for seven days – but no charges were ever brought.
Earlier this month the Guardian newspaper reported the Ministry of Defence is unlawfully holding 66,000 files that should have been declassified and transferred to the National Archive under the 30-year rule, including a large number of documents relating to the conflict in Northern Ireland.
Mr Dallat said: "The Army files stored in a warehouse in England must be brought back and sifted through for clues of the extent of the collusion."
Last week, a new book – Lethal Allies British Collusion in Ireland – by Pat Finucane Centre case worker Anne Cadwallader, claimed RUC officers and members of the UDR were part of a gang operating from two farms in south Armagh and Tyrone that killed 120 people between 1972 and 1976.
On October 30, 1993, UDA men Torrens Knight, Stephen Irwin, Jeffrey Deeney and Brian McNeill shot dead eight people in the Rising Sun Bar in Greysteel. The victims were: John Burns, Moira Duddy, Joe McDermott, Victor Montgomery, James Moore, John Moyne, Stephen Mullan and Karen Thompson. Nineteen others were injured.