Times+ for £5

The discussions took place in January, and were somehow leaked to Paul Staines, a longstanding critic of Labour who blogs under the name Guido Fawkes.

After news of the e-mails emerged, the former Home Secretary Charles Clarke – one of Labour’s “big beasts” – waded in by accusing Mr McBride of shaming the party and urging his removal, which was confirmed several hours later.

Mr McBride, who has been with Mr Brown since his Treasury days, said in a statement that he was shocked and appalled at the way the e-mails had been used, and regretted any embarrassment caused to the Government.

A Downing Street spokesman said: “Neither the Prime Minister, nor anybody else in Downing St, had knowledge of these e-mails.

“It is the Prime Minister’s view that there is no place in politics for the dissemination or publication of material of this kind, which is why it is right that Mr McBride and Mr Draper took the decision not to publish this material and regrettable that others are choosing to do so.”

Mr McBride added: “I have already apologised for the inappropriate and juvenile content of my e-mails, and the offence they have caused, but I did not want these stories in the public domain – it is because Paul Staines has put them there, and I am sickened that he has done so.

“However, we all know that when a backroom adviser becomes the story, their position becomes untenable, so I have willingly offered my resignation.”

Mr McBride was the Prime Minister’s political spokesman until last October, when he was shifted to become head of strategic planning at No 10 amid criticism of his handling of Ruth Kelly’s resignation.

Mr Staines – who has had a long-running spat with Mr McBride – welcomed the aide's departure, and rejected criticism that he had caused the problem by obtaining and revealing the nature of the material.

“It raises questions about how Labour operates,” he told Sky News. “This kind of smearing, pouring poison in journalists’ ears. I think Damian was using it to destroy Labour politicians, never mind opponents. “That [tactic] is gone now. That was the 1990s.”

Mr Draper said that Mr McBride was paying a high price for material that he had chosen not to publish. “They were never published on a website,” he said. “I do not think they would ever have been published on a website... that kind of thing is not right.”

He went on: “You have to wonder just for having an idea, even though it was a silly idea, whether someone deserves to lose their job. It is a very heavy price to pay for something that never actually happened.”

Liam Byrne, the Cabinet Office Minister, dismissed Mr McBride’s smear suggestions as “scribble”, and said that he had done the “honourable thing”.

“Once Mr McBride had scribbled this stuff and exchanged it with [Derek Draper] I think he concluded that actually either Mr Draper’s website and indeed the public at large didn’t need this stuff, didn’t deserve it, it was not something that should have been waved in the public’s face, and indeed belonged in the bin," he said.

“That was the decision that he took, so it is actually through the decisions of others who are determined that it should come into the public domain that we have heard about this news.”

Times Recommends

• Milk: do we need a dairy godmother?
• DIY: the women doing it for themselves
• First double portrait of Princes unveiled