A unionist negotiator at the 2001 talks which resulted in a promise of a public inquiry into the murder of Pat Finucane says the behaviour of republicans at the time “released HM Government and other parties from any moral or legal requirement” to follow through on the pledge.

David Campbell, a former UUP chairman and talks negotiator at Weston Park, says the Northern Ireland Secretary of State is wrong “when he attempts to justify his sop to the republican movement as fulfilling a UK Government commitment given at” the talks.

Hilary Benn has argued that the “exceptional reason” which justified a full public inquiry into the UDA murder was that the government had promised it in its agreement with the Irish Government at Weston Park, and latterly to the House of Commons.

Mr Campbell told the News Letter: “Unlike the Secretary of State, I was present at Weston Park as one of the unionist negotiators.

placeholder image — Sinn Fein Health Minister Bairbre de Brun in the Sinn Fein office at Stormont after it was searched by police in 2002. The raid was part of an investigation into a republican spy ring, and the events promoted the collapse of the fledgling Assembly amid unionist concerns about republicans' commitment to peace. Photo: Paul Faith/PA Wire

"It is true that commitments were given that a limited number of public inquiries would be granted and we tried to balance some of the absurd Republican demands with inquiries of importance to unionism and loyalism.

“However, the Weston Park (and subsequent negotiations) outcomes were all predicated on the republican movement (PIRA and SF) fulfilling its commitments under the Belfast Agreement, ending all violence, and participating as democrats in the resumption of devolved partnership government.

"In practice in little over a year the PSNI uncovered a republican spy ring working out of Parliament Buildings, Stormont and the most promising period of devolution ended abruptly. Moreover in the following months and years the Republican movement was to carry out at least three murders.

“These breaches of the agreements at Weston Park were profound and solely the responsibility of republicans, and they released HM Government and other parties from any moral or legal requirement to carry through other commitments.

“The granting of this inquiry is wrong and a further insult to the families of the many innocent victims of terror”.

Pat Finucane, a criminal defence lawyer from Belfast, was murdered by loyalist terrorists in front of his wife Geraldine and his children at their home in the north of the city in 1989. His son John, also a solicitor, has gone on to be elected as the Sinn Fein MP for North Belfast.

The family have long argued there was collusion between the Ulster Defence Association (UDA) gunmen and elements of the state

A review by Sir Desmond de Silva, published in 2012, expressed significant doubt as to whether Mr Finucane would have been murdered by the UDA had it not been for the different strands of involvement by elements of the state. It found “a series of positive actions by employees of the state that actively furthered and facilitated his murder and that, in the aftermath there was a relentless attempt to defeat the ends of justice”.

However, it found that “each of the facets of the collusion” that were found – the passage of information from members of the security forces to the UDA, the failure to act on threat intelligence, the participation of state agents in the murder and the subsequent failure to investigate and arrest key members of the West Belfast UDA – can each be explained by “wider thematic issues”.

In his speech to the House of Commons on Wednesday, Hilary Benn was challenged by the Tory shadow NI secretary on the potential costs of the new inquiry.

The Labour minister had said that it is the government’s “expectation that the inquiry will - while doing everything that is required to discharge the State’s human rights obligations - avoid unnecessary costs given all the previous reviews and investigations, and the large amount of information and material that is already in the public domain”.

He pointed to recent High Court proceedings, where he said the judge suggested that an inquiry could “build on the significant investigative foundations which are already in place”.

Gavin Robinson this week put the cost of previous investigations at £20m. The DUP leader said: “In 2004, a man was convicted and sentenced for his role in the murder and more than £20m has been spent on investigations into this one murder. “The Secretary of State needs to understand that there are more than one thousand other families in the United Kingdom who have not had a fraction of the resource poured into the murder of their loved one. Indeed, the Finucane family were offered a public inquiry, but they rejected that offer as they disagreed with the 2005 Public Inquiries Act”.