Oliver Dowden has resigned as chairman of the Conservative Party after it suffered two by-election defeats, saying in a letter to Prime Minister Boris Johnson that "someone must take responsibility".
Mr Dowden's resignation came at 5.35am, shortly after the announcement of the two defeats. He had been scheduled to appear on the morning media round before he decided to step down.
In Tiverton and Honiton the Liberal Democrats overturned a 24,000 Tory majority to win, while Labour reclaimed Wakefield.
The contests, triggered by the resignation of disgraced Tories, offered voters the chance to give their verdict on the Prime Minister just weeks after 41 per cent of his own MPs cast their ballots against him.
Mr Dowden said in his letter to the PM the by-elections "are the latest in a run of very poor results for our party".
"Our supporters are distressed and disappointed by recent events, and I share their feelings.
"We cannot carry on with business as usual. Somebody must take responsibility and I have concluded that, in these circumstances, it would not be right for me to remain in office."
The MP ended his letter by saying: "I want to emphasise that this is a deeply personal decision that I have taken alone.
"I will, as always, remain loyal to the Conservative Party."
A dramatic swing of almost 30 per cent from the Tories to the Liberal Democrats saw Richard Foord secure a majority of 6,144 in Tiverton and Honiton.
The new Lib Dem MP used his acceptance speech to call for Mr Johnson "to go, and go now", claiming his victory had "sent a shockwave through British politics".
Mr Foord said: "The people of Tiverton and Honiton have spoken for Britain. They sent a loud and clear message - it's time for Boris Johnson to go, and go now."
He said that "every day Boris Johnson clings to office he brings further shame, chaos and neglect".
Lib Dem leader Sir Ed Davey said: "This should be a wake-up call for all those Conservative MPs propping up Boris Johnson.
"They cannot afford to ignore this result."
He said it was "time for Conservative MPs to finally do the right thing and sack him".
'Boris Johnson, your contempt for this country is no longer tolerated'
A Tory source said it was a "disappointing but not unexpected result" and "we are confident we will regain this seat at the next general election".
In Wakefield, Simon Lightwood was elected with a majority of 4,925 on a swing of 12.7 per cent from the Tories to Labour.
The previous Wakefield MP Imran Ahmad Khan quit after being found guilty of sexually assaulting a 15-year-old boy - a crime for which he was jailed for 18 months.
Wakefield was one of the so-called red wall seats won by the Tories in the 2019 general election after being Labour since the 1930s.
Mr Lightwood said: "The people of Wakefield have spoken on behalf of the British people.
"They have said, unreservedly: Boris Johnson, your contempt for this country is no longer tolerated."
Labour leader Sir Keir Starmer said: "Wakefield has shown the country has lost confidence in the Tories.
"This result is a clear judgment on a Conservative Party that has run out of energy and ideas. Britain deserves better."
He said the result showed Labour "is back on the side of working people, winning seats where we lost before, and ready for government".
Mr Johnson, who is at a Commonwealth leaders' summit in Rwanda, suggested it would be "crazy" for him to quit if the party lost the two seats and said mid-term by-elections were "never necessarily easy for any government".
Here is his resignation letter in full...
Dear Prime Minister,
It is with great sadness that I must resign as Chairman of the Conservative Party with immediate effect.
Yesterday's Parliamentary by-elections are the latest in a run of very poor result for our party. Our supporters are distressed and disappointed by recent events, and I share their feelings.
We cannot carry on with business as usual. Somebody must take responsibility and I have concluded that, in these circumstances, it would not be right for me to remain in office.
It has been an honour to serve in your Cabinet as Party Chairman, Culture Secretary and Minister for the Cabinet Office. In particular, I want to take this opportunity to pay tribute to our excellent Conservative volunteers and staffers who work so tirelessly for our cause. They are the backbone of our great party and deserve better than this.
Finally, I want to emphasise that this is a deeply personal decision that I have taken alone. I will, as always, remain loyal to the Conservative Party.
Rt Hon Oliver Dowden CBE MP