A former Northern Ireland Office official has defended the fact he told Republicans they were not wanted for prosecution, saying letters were only sent after the office was told checks had been made by police.

Mark Sweeney, who headed the NIO's Rights and International Relations Division between 2004 and 2007, said the office was told by the Police Service of Northern Ireland that full checks had been made and so the letters were sent in good faith.

In 2007, Mr Sweeney signed a letter telling John Downey he was not wanted for prosecution. The letter eventually led to the Old Bailey preventing his trial on murder charges for the 1982 Hyde Park bombing.

Mr Sweeney told the House of Commons Northern Ireland Affairs Committee he had no knowledge of who John Downey was at the time. He said he fully accepted the Downey letter should not have been sent because Mr Downey was wanted by the Metropolitan Police. He regretted that it had been sent.

Mr Sweeney said he was told by the PSNI that Mr Downey was not wanted, but it turned out there had not been a full check on Mr Downey with British police forces.

Mr Downey had been listed as “wanted” the year before letters were sent, but Mr Sweeney said it would not have been appropriate to have questioned the PSNI on why an individual’s case had been reviewed.

Mr Downey was not the only person whose status changed from "wanted" to "not wanted" after the PSNI set up Operation Rapid in 2007 in response to demands by Tony Blair that the issue be sorted out before he left Downing Street that June.

The Attorney General’s Office had written to the NIO because it had received 25 names of people who were no longer wanted and it sought to ensure UK-wide checks had been made, said Mr Sweeney.

That, he said, led him to query the situation with the PSNI who confirmed full checks had been made and “that they were the same ones that had been done” in the past, Mr Sweeney told MPs.

Responding to questions from Alliance MP, Naomi Long, Mr Sweeney said the AG’s office had queried the 25 names because it was the first list produced after Operation Rapid was set up and it wanted to be sure the same checks had been made as before.

The PSNI’s assurances to the NIO were given by the now-retired Assistant Chief Constable Peter Sheridan, on information he had been given by Detective Chief Superintendent Norman Baxter.

Saying that he had no “ill-will” for either man, Mr Sweeney said Mr Baxter had understood it was the PSNI’s role to be able to say whether someone was wanted in Northern Ireland and Great Britian.

Mr Sweeney and another official involved in sending out the so-called "On The Runs" letters, Dr Simon Case appeared for nearly hours before MPs, alongside NI Secretary of State, Theresa Villiers and the NIO's top official, Jonathan Stephens.

Ministers had never brought pressure to bear on officials to try to get the status of some OTRs changed, Mr Sweeney said, though there was frustration occasionally that not enough PSNI officers were detailed to carry out check on cases.

However, Jonathan Stephens insisted that the PSNI had known that “not wanted” OTRs were getting assurances that they were not facing prosecution, though SF wanted those facing charges to be given a no prosecution guarantee too.