"Since I became Prime Minister, I've said there should ne no election until 2020, but now I have concluded that the only way to guarantee certainty and security is to hold this election and seek your support for the decisions we must take".
She says Labour has threatened to vote against the final deal, and the Liberal Democrats want to bring parliamentary business to a standstill.
European Council President Donald Tusk tweeted that he had a "good phone call" with May about the election, and the council said the bloc's Brexit plans were unchanged by the announcement.
In order to call the early election, she will need the support of two-thirds of the 650 MPs in the Commons - but Labour is expected to support her, as any opposition would look weak if it did not agree to the chance to take office.
Britain´s next election was due to have been held in 2020 - a date enshrined in legislation according to which elections have to be held every five years in May.
So tomorrow in the House of Commons I will call for an election on the 8th of June.
"If this general election is about leadership, as Theresa May said this morning, she should not be dodging head-to-head TV debates", Labour leader Jeremy Corbyn said.
"We believe that the country does need stability during the time ahead and a leader that can deliver a Brexit which is for the benefit of everyone in the UK".
However, a 2011 law passed by Cameron during his coalition government with the Liberal Democrats has complicated matters. It will also enable her to set her own policy agenda rather than be bound by that on which Mr. Cameron built his electoral platform in 2015, the year before the Brexit referendum.
"As we move through this period of national change, voters across the United Kingdom will face a choice between the leadership of Theresa May or the chaos and incompetence of Jeremy Corbyn".
Scotland's First Minister Nicola Sturgeon said she would be fighting the election "to win".
When asked who they thought would be the best prime minister, 50 percent of respondents in the YouGov poll said Theresa May and only 14 percent Corbyn.
He was speaking after Theresa May's shock announcement that she would move to hold a national poll on 8 June.
The 60-year-old vicar´s daughter is Britain´s second prime minister after Margaret Thatcher and many commentators have drawn comparisons to the steely determination of the "Iron Lady".
But some of the UK's other political parties are against the move and have promised to fight her Conservative Party.
'There is nothing you can do about it and if there are ups and down in the market or in Sterling over the next few weeks and months those ups and downs are utterly irrelevant long-term, ' he said.