Seamus Maguire is thought to have been killed and secretly buried by republican paramilitaries between 1973 and 1976.

The Independent Commission for the Location of Victims’ Remains said they searched 26 acres of Bragan Bog in Co Monaghan for Mr McVeigh.

Mary-Lou McDonald was speaking following reports a Sinn Fein member had been named as involved in the disappearance of Columba McVeigh in 1975.

Mr Lynskey, a former monk from Belfast who later joined the IRA, was abducted, murdered and secretly buried by the IRA in 1972.

The British Army officer is believed to have been abducted by the Provisional IRA while on an undercover operation in a pub in south Armagh in 1977.

A decision to end the sixth search for the teenager killed and secretly buried by the Provisional IRA has been described as ‘bitterly disappointing’.

Dympna Kerr also appealed for fresh information to help find her brother.