May ruled out participating in televised debates with other leaders.
Labour leader Jeremy Corbyn retorted: "We welcome the General Election but this is a Prime Minister who promised there wouldn't be one, a Prime Minister who can not be trusted".
Speaking to the Sun, Mrs May revealed a concern that the May 2020 election date stipulated by the Fixed-Term Parliaments Act would leave her vulnerable to pressure from Brussels as she neared the end of the two-year withdrawal negotiations in March 2019.
Keith Wade, chief economist at fund manager Schroders, said: "A successful election would give May the mandate to pursue her own Brexit strategy".
"The worst may be behind us", the bank's analysts said.
"I want this country to be able to play the strongest hand possible in those negotiations to get the best possible deal because that's in our long-term interests".
There'll be a debate in the Commons later followed by a vote, which needs a two thirds majority to go through. Why are we voting again? "We look forward to showing how Labour will stand up for the people of Britain".
May's Conservatives now hold 330 of the 650 seats in the House of Commons.
While opposition parties have criticised the u-turn, both Labour and Liberal Democrats are expected to vote in favour of the election, giving easily enough support to pass the motion.More news: US tells North Korea: We don't want a fight, don't start one
LEDBURY'S MP, Bill Wiggin has welcomed the prospect of a snap general election, saying it is the only way to limit uncertainty and instability in the run up to Brexit.
"I think the difference is in Scotland we've kind of always done them", she said. "If you put all those things together they equal a general election".
While some market uncertainty is expected in the short-term, advisers argue a bigger mandate for the Conservative party would give more clarity on the direction the United Kingdom will take in its Brexit negotiations.
If the election goes ahead, parliament would be dissolved on May 3 and the campaign would begin in earnest, just days after European Union leaders hold a special summit to agree a negotiating strategy for Brexit on April 29.
Following considerable wrangling over formats, the 2015 election campaign saw one debate featuring Mr Cameron and Mr Clegg alongside Labour's Ed Miliband and leaders of Ukip, the Scottish National Party, Greens and Plaid Cymru, as well as a second debate with the five non-coalition parties and programmes in which Mr Cameron, Mr Clegg and Mr Miliband answered questions but did not debate face-to-face. But John McDonnell, the shadow chancellor, told the BBC that although people feel the election is unnecessary, he "honestly believes Labour will form a government".
Polls give May's Conservatives a double-digit lead over Labour, which could have its worst election showing in decades. A national election in May 2015 was followed by the June 2016 referendum on European Union membership.
Liberal Democrat leader Tim Farron said that broadcasters should hold debates anyway, with an empty chair in May's place.
He also hinted at a raft of radical policies to be unveiled by Corbyn, including more taxes on big corporations and the rich - defining this group as those who earn more than £70,000 to £80,000 a year.