Staff members start to count votes at a polling station in Sunderland, Britain on June 8, 2017. [Photo/Xinhua]

Labour's Emily Thornberry, the shadow foreign secretary, said late Thursday night May should consider her position if the exit poll proves accurate.

Speaking on Sky news, Thornberry said: "I think she should go. I think we're (Labour) on the verge of a great result." Labour's Shadow Chancellor John McDonnell also said he thought May's position would be untenable on the result of the exit poll.

May's expected losses come after the 100-plus wins predicted early on in the campaign.

In the run-up to the general election May had insisted that there would be no general election until the parliamentary term ended its five-year span in 2020.

She changed her mind, saying she wanted more support in her negotiations over the terms for Britain leaving the European Union.

Brexit, though, has not dominated the election campaign which was overshadowed by Britain's worst terrorist strike since 2005, with the detonating of a bomb by a suicide bomber at the end of a concert by singer Ariana Grande at the Manchester Arena.

Then came a second attack on London Bridge by three terrorists who were shot and killed within minutes by armed police.

May's manifesto also included controversial plans to cut heating allowances to pensioners and also reducing the guaranteed annual increase in their pensions. It also included a move that would see using the value of their homes to pay for care in their old age, dubbed by critics as the dementia tax.

The exit poll will also provide some comfort to Labour leader Jeremy Corbyn. At the start of the campaign a landslide of Labour losses had been predicted, weakening Corbyn's role as leader. But in the final weeks of the campaign the gap between the two leaders narrowed. For Corbyn the gap was a bridge too far to cross, but it is likely to weaken the hand of his critics, including many of her own MPs, who have wanted him to go.

Political commentators are already saying May's gamble in calling a snap election will turn out to be a disaster for her if the actual results reflect the exit poll.