The claim – which will be broadcast across the UK on BBC Two by one of the most respected journalists to have covered the Troubles – has come from intelligence sources north and south of the border.

Mr McGuinness has strenuously denied the allegation contained in veteran British journalist Peter Taylor's 10 Days of Terror documentary, the latest programme in his The Age of Terror series.

Last night Mr Taylor told the News Letter that it was victims of the 1987 bomb who had alleged to him that Mr McGuinness was involved when he was filming for the documentary last November.

"They first raised Martin McGuinness with me and I then went away and spoke to intelligence sources," he said.

"All sources, both north and south of the border, came up with the same thing – that Martin McGuinness was the leading figure in the IRA's Northern Command at the time."

And in the programme, PSNI Detective Chief Superintendent Norman Baxter said that Northern Command knew about the plan to bomb the Remembrance Day service.

Investigation

The senior officer, who led the investigation into the bombing, told the programme that it was not an unauthorised, one-off operation by a local IRA unit but was carefully co-ordinated as part of a "strategy of genocide" by three IRA units – two from the Republic and one from Northern Ireland.

He said that prior to the bombing there were deliberations at a very senior level within the IRA and that its Northern Command knew of the operation.

"The calculation was taken as to the number of casualties they could inflict on the civilian population against the number of casualties they could inflict on members of the security forces – and they decided the risk was worth taking," he said.

Mr Baxter also pointed out that the IRA planned a simultaneous attack on a Boys' and Girls' Brigade parade at the border village of Tullyhommon a few miles away but the bomb failed to go off.

The bomb exploded without warning at the cenotaph at 10.43am and among the dead – all of whom were civilians – were three married couples, a retired policeman and a nurse.

The programme also reveals the contents of a secret intelligence document detailing the weaponry given to the IRA by Libyan leader Colonel Muammar Gaddafi.

Interception

The paper reveals the scale of the arms shipments landed in Ireland prior to the interception of the mV Eksund vessel seized while taking arms from Libya to the IRA.

The arsenal included 36 rocket launchers, 10 surface to air missiles, 26 heavy machine guns, more than 200 grenades, 10 flame throwers and vast quantities of Semtex explosive.

Last night Mr Taylor said that his interviews with victims of the bomb were some of the most moving he has ever conducted.

Some of the victims had words of praise for Mr McGuinness.

Speaking of his position as Deputy First Minister, Joan Wilson, whose daughter Marie died in the attack, said: "I regard him as a good politician.

"We all learn from experience. But it was a big step for him too and I wish him well."

Mr McGuinness dismissed the claim he was the leading figure in the IRA's Northern Command as "a securocrat fantasy".

"The allegations made in this programme are completely false and are entirely based on untrue briefings from faceless individuals in the intelligence apparatus long hostile to Sinn Fein," he said.

The Age of Terror is broadcast on BBC Two tonight at 9pm.