David Cameron has announced his resignation.
The Prime Minister said he will have left the post before the Conservative Party Conference in October.
The shock announcement comes after Britain voted to leave the European Union.
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Mr Cameron said the result of the referendum meant "the country requires fresh leadership".
In an emotional speech outside 10 Downing Street, he said: "The British people have voted to leave the EU and their will must be respected.
"The will of the British people is an instruction that must be delivered.
"There can be no doubt about the result.
"Across the world people have been watching the choice that Britain has made.
"This will require strong, determined and committed leadership.
"I am very proud to have been Prime Minister of this country for six years.
"I have held nothing back.
"I think the country requires fresh leadership.
"I do not think I can be the captain to take the country to its next destination.
"In my view I think we should have a new Prime Minister in place by the start of the Conservative conference in October."
Kent's MPs have reacted to the shock revelation.
Sittingbourne and Sheppey MP Gordon Henderson said it wasn't a great surprise because of the overnight circumstances and the fact the Prime Minister had always made clear he would go by 2020.
"I think the country requires fresh leadership. I do not think I can be the captain to take the country to its next destination" - David Cameron
He said: "I was pleased about how he went about it in such a measured way, I thought that was the right thing to do.
"I was one of the 80-plus MPs who wrote to him yesterday and asked that he stay whatever the result."
Paying tribute, he said Mr Cameron should be remembered and thanked for delivering the referendum.
"Conservatives, me among them, have been banging on about Europe for years and David Cameron actually did what he promised and delivered a choice for the British people to make," he said.
Mr Henderson, who was first elected in 2010, wouldn't be drawn on who he would be supporting to succeed the PM.
But said he would imagine Boris Johnson, Michael Gove, Theresa May and possibly George Osborne would be putting themselves forward.
He also suggested some faces from the 2015 intake of Tory MPs might emerge as candidates.
If Mr Johnson was one of the two candidates whom party members had to vote on, he suspected he would win and would become PM.
Dartford MP Gareth Johnson was also not surprised by Mr Cameron's decision to step down.
He said: "This is clearly a new era for Britain.
"I always thought that David Cameron's departure was a possibility if we voted to leave the EU.
"Dartford voted overwhelmingly to leave the EU and I am proud to have supported this position too.
"We are today entering a new chapter but I feel strongly that leaving the EU will ultimately be a good thing for the UK.
"There will undoubtedly be difficult times ahead but it is essential we keep our nerve. Britain can stand proud today and look forward to a better future.
"We are strong enough to make a success of this new direction for our country and so we need to take this opportunity to move Britain forward."
Canterbury and Whitstable MP Julian Brazier is thrilled with the referendum result, but saddened by the Prime Minister's departure.
He said: "I'm obviously absolutely delighted that we have voted to leave the EU. I'm pleased that the people of Canterbury voted to leave.
"I am saddened by the Prime Minister's decision, but I can understand his resigning. He deserves huge credit for his victory at the election and I am proud to have served as part of his team.
"I signed a letter hoping he would stay. But I understand the decision he made."
Sevenoaks MP Michael Fallon ruled out standing for selection as the new Conservative leader.
The Defence Secretary told the BBC: "I'm certainly not putting my hat in the ring."
On the referendum result, he said: "The decision has been taken and we all have to make it work."
Meanwhile, Folkestone and Hythe MP Damian Collins would not be drawn on who he thought should take over from Mr Cameron.
"I don't think he [Cameron] had any alternative choice given the result and did the right thing for the country," he said.
"But he's not going to go straightaway and is going to give us the choice for someone new to lead the country.
"I think that's good because it gives us a chance for stability.
"I've got no view on who that might be at the moment, I think it's too soon but we need experience."
South Thanet MP Craig Mackinlay said Mr Cameron had invested too much personally in the referendum.
He said: "I am disappointed that he has resigned. He has been a good Prime Minister and has done a lot of good things.
"I do think that he invested personally too much political capital in the referendum when he did not need to do so.
"I do want to see a pro-Brexit Prime Minister but I am going to wait and see who will stand."
He rejected the claim that there should be a general election, saying there was no constitutional requirement to do so.
Herne Bay MP Sir Roger Gale said: "I am very sad indeed that the Prime Minister has taken the decision to resign, but I fully understand why as he is an honourable man and he made his position clearly known.
"In the interests of the UK, I don't feel it is a good thing because we will have a hasty leadership election and I think it is not beyond the bounds of possibility that we will find ourselves with an early general election.
"Unfortunately, when the economy of the UK sneezes, Thanet catches the cold because we are an area of high social deprivation and the moment the economy goes into a down turn, Thanet feels it more than others.
"I hope very much that the predictions that have been made are not realised but I fear they will be."
Ashford MP Damian Green said: "I did think that if there was a vote to leave then it was possible he could go.
"If there is to be a radical change in direction, the new Prime Minister should be the person who can get the best deal for Britain and do all the other things that we want from a Prime Minister."