The ombudsman detailed failures including several instances of police planning to arrest suspects but not following through.

Ten Protestant workmen were shot dead by the IRA outside the village of Kingsmill in 1976 in one of the most notorious incidents of the Troubles.

Ten Protestant workmen were shot dead in the sectarian attack by the IRA in Co Armagh in 1976.

A long running inquest into the 1976 atrocity last week criticised the IRA and its political representatives for not engaging with proceedings.

A little-known republican paramilitary group had claimed responsibility for the 1976 shootings.