PSNI chief constable Matt Baggott has said he stands by his apology following the collapse of the Hyde Park IRA bomb case.
The trial of John Downey, 62, for the 1982 blast, which killed four soldiers, was stopped because he mistakenly received a letter from the Government telling him he was not wanted by police.
In fact he was sought by the Metropolitan police but that was not communicated to him by officers in Northern Ireland.
A retired senior detective has dismissed any suggestion that an error was made by the Police Service of Northern Ireland (PSNI) and said the final letter included additions made by the Northern Ireland Office NIO.
Chief constable Matt Baggott said: "I am clear that the apology I gave in the aftermath of this judgment was appropriate.
"I stand by it."
Former detective chief superintendent Norman Baxter appeared before the Northern Ireland Affairs Committee on Wednesday to explain his role in the contentious on-the-runs administrative scheme, which saw letters sent to around 190 republicans informing them they were not sought by the authorities in the UK at that moment but did not rule out future prosecutions if new evidence emerged.
Details of the plan, which was agreed by Sinn Fein and the Government in the early 2000s as part of the peace process, emerged following the collapse of the case against Donegal man Mr Downey.
Names of individuals who feared they were wanted fugitives were passed to the Government, mostly through Sinn Fein, asking for an assessment of their status.
The Downey prosecution was stopped in February after a judge found he had been wrongly sent one of the so-called letters of comfort.
The message was sent by the NIO but was based on an assessment made by Mr Baxter that Mr Downey was not wanted by the police.
Separately, Mr Baxter alleged yesterday that Downing Street asked police in Northern Ireland to release two republican terror suspects hours after they had been arrested in connection with the attempted murder of a soldier.
Mr Baxter told the committee Sinn Fein president Gerry Adams had put pressure on Downing Street to ask for the release of Vincent McAnespie and Gerry McGeough, arrested for questioning about the attempted murder of part-time Ulster Defence Regiment soldier Sammy Brish in 1981.
McGeough was later convicted and sentenced for attempted murder.
The phone call from Government in 2007 was made at the request of Sinn Fein president Gerry Adams, Mr Baxter claimed.
Mr Adams has denied asking the Government to intervene with the PSNI.
Former chief constable and now Association of Chief Police Officers head Sir Hugh Orde has also said no such call was received from Downing Street, claiming he would have remembered it until his "dying day".
Mr Baggott said Mr Baxter should come forward with details behind his allegations and has written to the former officer asking him for his account.
He told the Policing Board in Belfast: "Mr Baxter will be asked to justify his comments."
He added: "It was a serious allegation made in the context of parliamentary privilege, we now want to assess exactly what the facts are.
"Once we have got that, if there is any further action necessary then we will take that forward."
Stormont justice minister David Ford separately defended his senior civil servant Nick Perry over claims the permanent secretary did not pass on information about the administrative scheme to him after he transferred from the NIO.
He said: "I completely reject the suggestion made during last week's (Justice) Committee meeting that my department is dysfunctional or that Mr Perry's actions have given me cause for embarrassment.
"I have a very good working relationship with Mr Perry and believe we carry out our respective roles as political and administrative heads of the department appropriately and effectively."
Lady Justice Hallett has been appointed by Prime Minister David Cameron to review the administrative scheme.