LONDON -- In a shock announcement, Prime Minister Theresa May on Tuesday called for an early general election to be held June 8 to seek a strong mandate as she negotiates Britain’s exit from the European Union.

Standing outside 10 Downing Street, May said she would ask the House of Commons on Wednesday to back her call for an election, three years before the next scheduled date in May 2020.

She said that since Britons voted to leave the EU in June, the country had come together, but politicians had not. She said the political divisions “risk our ability to make a success of Brexit.”

At present, May’s governing Conservatives have 330 seats in the 650-seat House of Commons. May said that, “our opponents believe that because the government’s majority is so small, our resolve will weaken and that they can force us to change course” on leaving the EU.

“They are wrong,” she said. “They underestimate our determination to get the job done and I am not prepared to let them endanger the security of millions of working people across the country.”

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Under Britain’s Fixed-Term Parliaments Act, elections are held every five years, but the prime minister can call a snap election if two-thirds of lawmakers vote for it.

The leader of the main opposition Labour Party, Jeremy Corbyn, said Tuesday he backed the call. Leader of the Liberal Democrats, the second-largest opposition party in Britain, also said he looked forward to fighting the parliamentary election.

Tim Farron, the Liberal Democrat leader, said his party was the only choice for the half of Britons who never wanted to leave the European Union, and who now want to avoid a “hard Brex,” which would leave the U.K. outside the EU trading bloc.

May took office in July after predecessor David Cameron stepped down following his failed attempt to get voters to back remaining in the EU. Since then she has ruled out calling an early election to get her own mandate. But she said Tuesday she had “reluctantly” changed her mind.

Polls give May’s Conservatives a double-digit lead on Labour, which is divided under left-wing leader Corbyn.

The pound rose 0.1 percent against the U.S. dollar after the announcement, to 1.257, recovering from a 0.4 percent drop an hour earlier.