Boris Johnson is promising to deliver Brexit and repay the trust of voters after he led the Conservatives to an “historic” general election win.
The prime minister – who will meet the Queen shortly to ask to form a new government – has a Commons majority of 78, with one seat still to declare.
He said he would work “flat out” and lead a “people’s government”.
BBC’s report quoted Jeremy Corbyn as saying that he would not fight another election as Labour leader, amid recriminations over the party’s defeat.
The opposition was swept aside by the Conservatives in its traditional heartlands in the Midlands and north-eastern England and lost six seats in Wales.
With just one constituency – the Cornish seat of St Ives – left to declare, the Conservatives have 364 MPs, Labour 203, the SNP 48, Liberal Democrats 11 and the DUP eight.
Sinn Fein has seven MPs, Plaid Cymru four and the SDLP has two. The Green Party and Alliance Party have one each.
The Brexit Party – which triumphed in the summer’s European Parliament elections – failed to win any Westminster seats.
The Conservative Party’s Commons majority is its largest since Margaret Thatcher won a third term in 1987.
In his victory speech, Mr Johnson told activists it was a “new dawn” for the country, echoing comments Labour’s Tony Blair made when he won the general election of 1997.
He thanked Labour voters, many of whom, he said, had backed the Conservatives for the first time, vowing to lead a “people’s government” and fulfil the “sacred trust” placed in him.
“You may intend to return to Labour next time round, and if that is the case, I am humbled that you have put your trust in me, and I will never take your support for granted,” he said.
“I will make it my mission to work night and day, flat out to prove that you were right in voting for me this time, and to earn your support in the future.”
Mr Johnson said the electorate’s “voice” had “been heard”, adding: “The people want change… We cannot and we must not let them down.”
Labour has suffered its worst defeat since 1935, losing seats across northern England, the Midlands and Wales in areas which backed Brexit in the 2016 referendum.
And Jo Swinson has quit as Liberal Democrat leader after losing her Dunbartonshire East seat to the SNP by 149 votes
Mr Johnson said the Tories’ thumping victory had “smashed the roadblock” in Parliament over Brexit and put an end to the “miserable threats” of another referendum on Europe.
He said: “We will get Brexit done on time by 31 January – no ifs, no buts, not maybe.”
Speaking after he was re-elected as MP for Uxbridge and South Ruislip, he said there had been a “political earthquake”.
During the six-week campaign, Mr Johnson – who became prime minister in July after a Tory leadership contest – focused relentlessly on a single message, to “get Brexit done”.
According to the BBC, Labour primarily campaigned on a promise to end austerity by increasing spending on public services.