By Ian Dunt
There were frantic scenes in Westminster today, as Andy Coulson resigned as director of communications at No 10.
The news of the statement came as Tony Blair delivered further evidence to the Iraq inquiry and Labour recovered from Alan Johnson's resignation yesterday.
There was considerable scepticism about the timing of the announcement in Westminster, as pundits assumed the government had picked a busy day to bury bad news.
The resignation is likely to raise questions about David Cameron's judgement. The prime minister stuck by his communications chief through years of negative news reports and gave him his full support.
It will also deprive Mr Cameron of a prized colleague who was respected for his intuitive understanding of the British public.
Mr Coulson said: "I can today confirm I have resigned as director of communications in Downing Street
"It's been a privilege and an honour to work for David Cameron for three and a half years."
The former editor said he was "extremely proud of the part he played" in getting the party back into government.
But he admitted the row over phone hacking made it "difficult to give the 110% needed in this role".
He added: "I stand by what I said about those events.
"When a spokesman needs a spokesman its time to move on."
Mr Cameron said: "I am very sorry that Andy Coulson has decided to resign as my director of communications, although I understand that the continuing pressures on him and his family mean that he feels compelled to do so.
"Andy has told me that the focus on him was impeding his ability to do his job and was starting to prove a distraction for the government."
The statement comes just days after the prime minister refused to deny reports that Mr Coulson had already offered his resignation.
Downing Street's director of communications has been in the spotlight throughout the long-running row over phone hacking at the News of the World, which he edited before joining the Conservatives.
A wide variety of public figures, from sports stars to politicians, are alleged to have had their phones hacked into.
The scandal led to the jailing of royal correspondent Clive Goodman. Mr Coulson resigned from the paper at that stage, although reports of the practise being far more widespread emerged afterwards.
The only time Mr Coulson commented about the affair under oath, during the Tommy Sheridan perjury trial last year, he reiterated that he had not known that the practise was widespread when he was editor.
The newspaper recently suspended news editor Ian Edmondson and launched an internal investigation. Meanwhile, the Crown Prosecution Service (CPS) announced it would re-examine all the evidence in the case.
As the political world started to debate the fall out of the resignation, questions were asked about who would replace Mr Coulson.
Guto Harri, a former BBC political correspondent and current spokesman for mayor of London, Boris Johnson was viewed as the frontrunner.
George Pascoe-Watson, the former political editor of the Sun who recently embarked on a career in public relations, was also considered.