Former British finance minister George Osborne said the exit poll forecasting that Prime Minister Theresa May will lose her majority in parliament would be "completely catastrophic" for her and the Conservative Party.
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"It is early days. It's a poll. If the poll is anything like accurate this is completely catastrophic for the Conservatives and for Theresa May," Osborne told ITV News.
"It's difficult to see if these numbers were right how they would put together the coalition to remain in office. But equally it's quite difficult looking at those numbers to see how Labour could put together a coalition so it's on a real knife edge."
The exit poll has predicted that May will win 314 seats, below the 326 needed to secure a majority.
Former Liberal Democrat leader Nick Clegg said on Thursday he could not see any circumstance in which his party would prop up a minority Conservative government in Britain.
An exit poll earlier suggested Conservative Prime Minister Theresa May could fall short of winning a majority in Thursday's election.
Asked by ITV if there was any circumstance in which the Lib Dems could prop up the Conservatives, Clegg said: "No."
The Lib Dems had nine seats in British parliament until Thursday's election. The exit poll projected they would win 14 seats this time.
The former communications director for Prime Minister David Cameron says the exit poll result will rock the Conservative Party.
Craig Oliver told Sky News that if the poll is accurate "there will be deep and lasting shock" in party headquarters as Prime Minister Theresa May's decision to call an early election seems to have backfired.
"It was the biggest gamble a politician has taken for a long time and if that exit poll is right, it's failed," he said.
Senior Labour Party adviser Emily Thornberry says that if the election exit poll is correct then Prime Minister Theresa May should consider resigning.
"If it's true, these are great results," she said. "If this is right, I think she should consider her position. I think she should go. She has manifestly failed."
Thornberry said May was guilty of showing "great hubris" when she called the snap election.
"She was 20 points ahead and thought she could do whatever she wanted with the country and we said, 'no' and we meant it."
Northern Ireland Secretary James Brokenshire says it is "too early to tell" if the exit poll showing the Conservative Party may not get a majority in Parliament will be accurate.
"We have to wait for some hard data," he said Thursday night, suggesting there seemed to be strong Conservative support in key marginal areas.
He defended Prime Minister Theresa May's decision to call an early election and predicted "a long night" before results are clear.