David Cameron has said he would not have hired Andy Coulson had he known what he knows now.
In a statement to the Commons the prime minister said that with "20-20 hindsight I would not have offered him the job".
"I hired Andy Coulson on the basis of assurances he gave me he did not know about hacking," Cameron told MPs.
He said if it turned out his former director of communications had lied to him then he would offer a "profound apology".
"Of course I regret, and I am extremely sorry about the furore it has caused. With 20:20 hindsight and all that has followed I would not have offered him the job and I expect that he wouldn't have taken it," he said.
"But you don't make decisions in hindsight, you make them in the present. You live and you learn and believe you me, I have learned."
Ed Miliband said Cameron had been caught in a "tragic conflict of loyalty" between his friendship with Coulson and the requirement to protect the office of prime minister and himself.
The Labout leader said the prime minister had been "compromised by his relationship with Mr Coulson" and that his office had therefore had to go out of its way to keep information about Coulson from him.
Miliband listed five occasions where Cameron's staff ignored information about the former News of the World editor and allegations that he knew about hacking.
"The country has a right to expect that the prime minister would have made very effort to uncover the information about Andy Coulson to protect himself and his office," he said.
"Yet the pattern of events suggests the opposite: that the prime minister and those around him made every effort not to hear the facts about Andy Coulson."
But Cameron said Miliband was engaging in "feeble conspiracy theories" and said Coulson had behaved impeccably while working in Downing Street unlike Labour spin doctors Alistair Campbell, Damian McBride and Miliband's current media adviser Tom Baldwin.
Pressed by Labour MPs on precise details of his relationship with Coulson as well as with other News International executives including Rebekah Brooks, Cameron said "looking for some secret behind the curtain that simply isn't there".


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