Poll results for Britain show Prime Minister Theresa May's Conservative government have fallen short of an absolute majority in the election.
The Tories are forecast to secure 314 seats in the 650-seat House of Commons, a loss of 17 seats from the 2015 election.
That would drop them below the 326 seats needed to form government outright.
Jeremy Corbyn's opposition Labour Party will win 260 seats, a possible boost of 28.
Ms May had called a snap election seven weeks ago, arguing that, after Britain voted to leave the European Union, it needed certainty, stability and strong leadership.
But opposition foreign-affairs spokeswoman Emily Thornberry has told the BBC it was a mistake and Ms May should now resign.
"She called this election when she thought that she was 20 points ahead in the polls. She said that she wanted to have a mandate for Brexit. She basically wanted to stamp out the opposition. She wanted to be able to have a blank cheque, a free hand, to do whatever she wanted with the country, in terms of Brexit negotiations, in terms of what she was doing to the National Health Service. And the country has said no."
Senior Conservative MP Ken Clarke says it is not in Britain's national interest to be left with a hung parliament, one where no party holds an outright majority.
"The worst outcome for the United Kingdom would be a weak government and a hung parliament, of any party, and we just have to see where we get. If we continue with another parliament with a small majority, then, firstly, we'll have to have some deeper debate than we had in the public debate during this general election on a lot of issues -- most particularly, Brexit. And, actually, as we face some appalling difficulties, in my opinion, this is a critical stage for us. Our politics is changing. There are huge problems. And perhaps a little more cross-party discussion and a little less of exchanging slogans ..."
The Scottish National Party is now expected to face a reduced representation in the lower house with 35 seats, with 12 potentially going to the Liberal Democrats.
Former Liberal-Democrats leader Nick Clegg has told ITV News the party has ruled out entering a coalition with either the Conservatives or Labour.
"The Liberal-Democrats fundamentally disagree, on a very basic level, with the design and approach, and architecture, of 'hard Brexit' taken by Theresa May over the last year and, indeed, endorsed by the Labour Party. So, there's just no meeting point between the Liberal-Democrats and the Conservative and Labour parties. Whatever happens, in whatever range of possibilities from this exit poll, it's clearly a complete boomerang election for the Conservatives."
The exit polls suggest the United Kingdom Independent Party, (UKIP) which campaigned heavily for withdrawing from the European Union, will not win any parliamentary seats.
Neil Hamilton, the UKIP (YOO-kip) leader in the Welsh Assembly, has tried to portray it hopefully, saying many of UKIP's voters supported the Prime Minister for one reason.
"After this disastrous election for the Conservatives, we'll be able to carve out a permanent niche for ourselves in UK politics as well, because we put forward a lot of policies in this election campaign which none of the other parties can copy us on, like slashing the non-humanitarian aid budget significantly to put money into the health service, scrapping green taxes to cut people's electricity bills. None of that really came out in this campaign, which was focused, I think, for UKIP supporters purely on the Brexit issue. And a lot of them have clearly gone to the Tories, without which Theresa May's position would have been very, very bleak, indeed."
