In a letter responding to the consultation on legacy matters, they said the £150 million earmarked for the Historical Investigations Unit (HIU) should be re-purposed.

A public consultation was launched earlier this year by Northern Ireland Secretary Karen Bradley on proposals to implement the four new legacy institutions set out in the 2014 Stormont House Agreement and the government’s manifesto for Northern Ireland 2017.

However, it has been met with scepticism from former Northern Ireland secretaries Lord King (1985-89) of the Conservatives and Lord Reid (2001-02), Lord Murphy (2002-05) and Lord Hain (2005-07) of the Labour Party.

Lord Hain said victim support should be resourced instead of “costly investigations that on past evidence would not deliver justice for victims”.

The four have also been supported by Lord Browne, Lord Eames, Lord Patten and Lord Cormack.

Their letter states: “We understand why many victims and others attach great importance to the prosecution, conviction and sentencing of those responsible for the appalling loss they have suffered. Their views clearly deserve the utmost respect.

“But experience suggests that it would be a mistake to expect that judicial outcome in any but a tiny percentage of the crimes that have not already been dealt with.

“Most of the cases were not easy to investigate immediately after they were committed and the passage of time - up to 50 years - has only made the chances of a successful outcome much less likely.”