Police have faced calls to act on the testimony of an anonymous IRA bomber who claims he knows who was behind the Birmingham pub attacks.

Unionist politicians in Northern Ireland demanded a response from officers in the UK and the Irish Republic after the man, identified only as Witness O, outlined the names to the ongoing inquests into the deaths.

He said he had been given permission to reveal the names in court of four men, three of whom are now dead, by the head of the IRA in Dublin.

DUP MP Sir Jeffrey Donaldson said the claims by Witness O must be pursued by the police.

The Lagan Valley representative insisted gardai in the Irish Republic had a role to play.

“One of the individuals named today has previously admitted involvement in the Birmingham pub bombings,” he said.

“This further evidence demands a proper police investigation into his involvement in the murder of 21 people.”

Sir Jeffrey also demanded answers from Sinn Fein, in particular its president.

“Mary Lou McDonald needs to explain how the head of the IRA in Dublin can give ‘permission’ for an individual to be named, when she tells us the IRA doesn’t exist,” he said.

He added: “Mary Lou McDonald should step forward and state clearly whether she believes the actions of the IRA in Birmingham and elsewhere were criminal.”

Ulster Unionist Assembly member Doug Beattie said: “Given that numerous Sinn Fein politicians have claimed that there is no IRA, you wonder just who is sitting in Dublin, claiming to be the head of it?

“The PSNI and the Garda need to give an assessment of this claim as a matter of urgency.”

Jim Allister, leader of the Traditional Unionist Voice party, asked: “Have the four named persons been investigated fully by the police and what further steps will now be taken?

“And, Mr (Leo) Varadkar, you who likes to mind everyone else’s business, what are you doing about the continuing operation of the IRA in your capital city under a ‘current head’? What actions have you taken, and will take, to address this issue?”

A West Midlands Police spokesman said: “The pub bombing investigation has never closed.

“Our approach is, where new facts come to light, they are scrutinised to see if people can be brought to justice.

“The force will never lose sight of the tragic fact that 21 people lost their lives in the atrocities that took place in Birmingham in 1974.

“It’s not appropriate to make further comment at this stage while we’re in the middle of the coroner’s inquests.”

A spokesman for the Garda in Ireland said: “An Garda Siochana do not comment on named individuals and on matters before the courts in other jurisdictions.”