Beleaguered Energy Secretary Chris Huhne quit David Cameron's Cabinet today after being charged with perverting the course of justice over allegations that he asked his ex-wife to take a speeding penalty for him.
In a letter of resignation to the Prime Minister, Mr Huhne said he was standing down as energy and climate change secretary to mount "a robust defence" against the charge. Remaining in the Cabinet would be "distracting" both to his legal fight and to his Government work, he said.
Deputy Prime Minister Nick Clegg said he hoped his Liberal Democrat colleague would "rapidly" clear his name to "return to play a key role in government as soon as possible".
In a letter to Mr Huhne, Mr Cameron said he had made "the right decision under the circumstances" and wished him well for the future. But the Prime Minister made no mention of a possible return to Government after the court case is concluded.
Mr Huhne's departure will force what is expected to be a limited Government reshuffle, with business minister Ed Davey tipped by senior sources for promotion into his former post.
The Eastleigh MP and his former wife, economist Vicky Pryce, who faces the same charge, will appear before Westminster Magistrates' Court on February 16.
The charge - which carries a maximum sentence of life imprisonment - will eventually be heard by a judge at Crown Court.
It is alleged that Mr Huhne persuaded his ex-wife to take penalty points for a 2003 speeding offence on his behalf to avoid losing his driving licence.
Mr Huhne announced his resignation in a 30-second statement outside his London home, less than an hour after Director of Public Prosecutions Keir Starmer announced the decision to charge him.
Describing the prosecution as "deeply regrettable", the 57-year-old MP said: "I am innocent of these charges and I intend to fight this in the courts and I am confident that a jury will agree."
Mr Huhne made clear that he will remain MP for Eastleigh in Hampshire while he awaits trial.
"So as to avoid any distraction to either my official duties or my trial defence, I am standing down, resigning, as Energy and Climate Change Secretary," he said.
"I will, of course, continue to serve my constituents in Eastleigh."
A spokeswoman for Osbornes solicitors, the legal firm representing Ms Pryce, said they were not commenting on the prosecution.
In his resignation letter to the Prime Minister, Mr Huhne said he was standing down "with much regret".
"I intend to mount a robust defence against the charges brought against me, and I have concluded that it would be distracting both to that effort and to my official duties if I were to continue in office," he wrote.
In reply, Mr Cameron praised his work as Energy and Climate Change Secretary, as well as his role in the negotiating the coalition between Conservatives and Liberal Democrats following the inconclusive 2010 election.
"I believe you have made the right decision under the circumstances," wrote the Prime Minister.
"You have made a very significant contribution to the Government, of which you can be justly proud...
"Like the Deputy Prime Minister, I am sorry to see you leave the Government under these circumstances and wish you well for the future."
In his letter, Mr Clegg told his former leadership rival he was "immensely grateful" for his "trailblazing" work in government.
The Deputy Prime Minister added: "I fully understand your decision to stand down from government in order to clear your name, but I hope you will be able to do so rapidly so that you can return to play a key role in government as soon as possible."
Full text of Mr Huhne's letter to Prime Minister David Cameron:
This letter is to submit with much regret my resignation as Energy and Climate Change Secretary. I intend to mount a robust defence against the charges brought against me, and I have concluded that it would be distracting both to that effort and to my official duties if I were to continue in office.
It has been an honour to negotiate and then serve in the first coalition government of modern times which has substantial achievements both in reducing the economic dangers faced by our country, and in making progress with policies to tackle climate change and provide energy security. Internationally, we have helped to build a coalition of ambitious countries in Europe and beyond to put the United Nations process back on track.
It has been a privilege to be a minister in the coalition government, and I wish the administration every success with the environmental and economic challenges that lie ahead.
Full text of Mr Cameron's reply to Mr Huhne:
Thank you for your letter informing me of your decision to resign from the Government. I believe you have made the right decision under the circumstances.
You have made a very significant contribution to the Government, of which you can be justly proud.
You were a member of the team which negotiated the formation of the Coalition Government between the Conservative Party and the Liberal Democrats in those crucial days after the General Election, with our shared commitment to come together as two distinct political parties and govern in the national interest.
As Secretary of State for Energy and Climate Change, you have led the Government's efforts to live up to its responsibility to tackle climate change with great passion and distinction. You played a key role in securing the progress made at the Cancun and Durban summits, and I pay tribute to the leadership you showed at both. You have been determined to deliver on our pledge that this should be the greenest Government ever, recognising that cutting carbon emissions is not a luxury but a necessity. And you have relentlessly championed green growth.
Thank you too for the important contribution you have made as a member of the National Security Council since its inception, not only on security of our energy supply, but also in our discussions on Afghanistan, and during the Libya campaign.
Like the Deputy Prime Minister, I am sorry to see you leave the Government under these circumstances and wish you well for the future.