James Purnell quits and calls on Brown to "stand aside"

12.55am: Hutton, Straw, D Miliband and Hoon have declared their support for Brown.

12.40am: Prescott attacks Purnell on LabourHome: "Not so much a Blairite as a careerite"

12.05am: Shaun Woodward tells BBC that he feels "badly let down" by Purnell. A few minutes earlier Peter Kilfoyle says Purnell has never held a proper job! These people will kill each other...

11.50pm: PM's full reaction: "The Prime Minister is disappointed by the resignation of James Purnell, of which he was informed shortly before 10 pm. His focus over the coming days will be on restructuring the Government on the big challenges facing the country for the future: how we guide the economy through the downturn and strengthen it for the future; how we push ahead with reform of and investment in our public services; and how we renew trust in our democracy and Parliament. He will continue to give his undivided attention to addressing these great challenges facing our country and putting the interests of the British people first and foremost." (From Paul Waugh).

11.45pm: David Miliband says he is NOT resigning.

11.38pm: LabourList saying Andy Burnham may quit tomorrow (thanks to commenter Dominic for the hat tip).

11.35pm Fraser Nelson: "Brown got rid of Blair by getting private secretaries to resign hour after hour. It seems Brown is going to go after ministers resign day after day."

11.20pm: George Osborne appears on Sky and then BBC News with two main messages:

• James Purnell's letter was all about what was in the interests of the Labour Party, not the country.
• Britain needs an election and the case for an election will be even stronger if Labour attempts to install another unelected Prime Minister.

11.20pm: Graham Allen MP calls on Brown to go - saying his view is shared by "most" Labour MPs.

11.10pm: PM says he is "disappointed" by resignation of Purnell but promises to restructure government over next few days and to give "undivided attention" to challenges facing Britain.

10.53pm: From CrownBlogSpot: Adam Boulton on Sky News says the "lights have gone out in Downing Street":

10.50pm David Cameron's reaction: "In a deep recession and a political crisis we need a strong united Government. Instead we have a Government falling apart in front of our eyes. Britain deserves better than this. With this resignation the argument for a general election has gone from being strong and powerful to completely unanswerable. For the sake of the country Gordon Brown must carry out the one final act of authority left open to him, go to the palace and call the general election we have been demanding.”

10.45pm: Michael Crick says Alan Johnson has campaign in place. Gerry Sutcliffe MP (Sports Minister) will run it if Johnson pulls trigger.

10.40pm: Full Purnell letter via PoliticsHome (click to enlarge):

10.35pm: Coffee House reports rumour that David Miliband may quit tomorrow. If true it is curtains for Brown.

The BBC has more.