Charges against three men accused of involvement in a spy-ring at Stormont were not dropped as part of a deal with the IRA, Tony Blair has said.
Police raided Sinn Fein offices at Stormont in October 2002
The prime minister was responding to a question asked by DUP deputy leader Peter Robinson during prime minister's question time.
Last week the three men who were arrested in 2002 were acquitted of all charges in connection with the case.
He said the decision was made by the Director of Public Prosecutions alone.
Mr Blair said no government minister had anything to do with the decision not to proceed with the prosecution.
Mr Robinson had said there were three theories as to why the case against the men had not gone ahead.
He said these were: That there was insufficient evidence against the men; that the government had done a deal with the IRA; or that the government was protecting sensitive, if not embarrassing, evidence and agents.
Mr Blair said that the conspiracy theories owed very little to the facts and a lot to the desire of people to stir up difficulty.
He added that while he could not comment on two of the theories put forward by Mr Robinson, it was completely untrue to say that there had been a deal done with the IRA.
Earlier, in response to a question asked by DUP leader Ian Paisley, the prime minister said he did not know why the DPP had decided not to prosecute.
However, he said he would be "happy to see" how much more information about the decision to free the men could be put in the public domain.
Peter Hain said he did not see the need for a parliamentary statement
"This was not a decision taken by any minister, neither was there any political interference in that decision," Mr Blair told the Commons on Wednesday.
"The decision to prosecute is taken by the DPP and the DPP has decided not to proceed with it.
"I don't know myself the reasons for that, I simply know that is what is decided.
"I will, however, look and see whether, consistent with the proper legal procedures, we are able to give more information.
"But it was a decision taken solely on the authority of the prosecuting authorities."
Earlier this week, Northern Ireland Secretary Peter Hain said he saw no reason for a parliamentary statement on the collapse of the Stormont "spy-ring" case.
Delegations from the DUP, the UUP and the nationalist SDLP held separate meetings on Wednesday with Attorney General Lord Goldsmith to demand clarification of the reasons why the charges were dropped.
Speaking after his party's meeting, SDLP leader Mark Durkan said the lack of certainty over the issue was deeply damaging.
"The attorney general has said it was not for lack of evidence... but the public interest was the reason," he said.
"When we pressed him that he needed to explain not just to us but to the public what that interest was, he said that to do so would actually cause more damage than the prosecution would.
"(This) must indicate that they regard the reason as being very dangerous information."
The three men were arrested following a police raid on Sinn Fein's offices at Parliament Buildings on 4 October 2002, when documents and computer discs were seized.
The arrests led to the power-sharing executive at Stormont being suspended, after the DUP and Ulster Unionists, led at that time by David Trimble, threatened to collapse the executive with resignations.
The Public Prosecution Service would not clarify what it regarded as the nature of the public interest which led to the charges being dropped.