Jeremy Corbyn has called on Theresa May to resign as election results point to a hung Parliament.
Speaking following his re-election as the MP for Islington North, the Labour leader said people had voted “for hope for the future”.
And he pledged that Labour MPs would make sure the policies in the party’s manifesto were “put before Parliament”.
Earlier, the party’s shadow foreign secretary claimed Labour could form a minority government.
Mr Corbyn, who won his seat with more than 40,000 votes, said at the election count: “The prime minister called this election because she wanted a mandate. Well the mandate she’s got is lost Conservative seats, lost votes, lost support and lost confidence.
“I would have thought that’s enough to go, actually, and make way for a government that will be truly representative of all of the people of this country.”
Labour has taken seats from the Conservatives including Battersea and Canterbury and have unseated former Lib Dem leader and Deputy Prime Minister Nick Clegg in Sheffield Hallam. And the party made gains in Scotland included regaining ex-PM Gordon Brown’s former seat of Kirkcaldy and Cowdenbeath.
A BBC projection forecasts 267 seats for Labour, up 35 compared with its 2015 result.
The Conservatives were projected to win 318, which would leave them short of an overall majority.
With an overall majority for the Conservatives possible but not certain and Labour behind them, shadow foreign secretary Emily Thornberry said: “Obviously we’re disappointed if we’re not able to form a majority government.”
But she added: “For us to have come from such a long way back, supposedly, to be in a position where we could form the next government is an extraordinary performance on behalf of the Labour Party and shows what we can do when we unite.”
Ms Thornberry was asked how Labour would able to form a minority government instead of the Conservatives and responded: “We would put forward a Queen’s Speech and a Budget. Our Labour MPs would vote for it and we would call on the other parties to vote for it as well.”
If they did not: “It would then be up to them, wouldn’t it, to explain to their constituents how it was that when given the choice, they let the Tories back in again.”
SNP leader Nicola Sturgeon spoke during the election campaign of a desire to form a “progressive alternative” to the Tories and supporting Labour on a “case by case” basis if the numbers added up. However, Labour leader Jeremy Corbyn ruled out a formal deal with the SNP.
Responding to the exit poll, Green Party co-leader Caroline Lucas said: “Any Green MPs elected tonight will do all they can to keep the Tories from Number 10, and back a Labour-led government on a case by case basis.”
However, the Liberal Democrat press office tweeted: “We are getting a lot of calls so just to be clear: No coalition. No deals.”
Polling expert Peter Kellner said early results indicated the Conservatives had done better than the exit poll predicted and Labour worse.
It comes at the end of a campaign that has seen Mr Corbyn address thousands at a series of campaign rallies.
But local candidates reported voters voicing doubts about his leadership on the doorstep.
In the 2015 general election, Labour won 232 seats under former leader Ed Miliband, down from the 258 seats secured in 2010.
It went into the 2017 election with 229 seats.
When Prime Minister Theresa May announced the election in April, her Conservative Party had a big double-digit lead in many polls and hoped for a landslide victory. However, the campaign saw the Tories’ poll lead narrowing.
Labour deputy leader Tom Watson called the early results “very promising for Labour” and called Mrs May “a damaged prime minister whose reputation may never recover”.
Mr Watson said he thought Mr Corbyn’s leadership of Labour was safe. “It would be very foolish for anyone to want to stand down in the Labour Party tonight after this result.”
But he added: “I can see Boris Johnson sharpening the knives for Theresa May after this result.”