She said the early ballot would strengthen Britain's negotiating hand with the 27-member EU.
Lawmakers voted Wednesday by a resounding 522 to 13 to back May's call for an election, easily surpassing the two-thirds majority in the 650-seat House of Commons needed to trigger an early vote.
With May seen winning a new five-year mandate and boosting her majority in Parliament by perhaps 100 seats, the pound held close to six-and-a-half month highs on hopes she may be able to clinch a smoother, more phased departure from the European Union and minimize damage to the United Kingdom economy.
In the last equivalent snap poll, in 1974, then Conservative Prime Minister Edward Heath called an election on the question of "Who governs Britain?" while he was battling striking coal miners.
During a special debate in theHouse of Commons, she said it was the "right and responsible" thing to do hold the election now to provide "five years of stability and certainty" and help the United Kingdom prepare for life outside the EU.
A Tory source said: 'All Conservative candidates will have to stand on the manifesto - it will lock them in and provide a much stronger mandate.
"If you look at the timetable, had the election been in 2020 we would have been coming up to the most crucial part of the negotiations, at the end of the negotiations, in what would be starting to be the run-up to a general election".
But under the timetable for the proposed general election, Parliament will be dissolved on May 3 which means there would be no House of Commons for the new MP to be elected to.
"And it's about sticking to our plan for a stronger Britain that will enable us to secure that more stable and secure future for this country and take the right long-term decisions for the future".
"She expects a coronation and not a contest", Farron said, urging voters to back his strongly pro-EU party to stop a Conservative landslide.
In Bolton, Mrs May said the country now has a "unity of purpose" and a desire for the Government to "get on" with implementing Brexit and "making a success of it". "We intend to review our sterling forecasts in coming days", they said.
Polls give the Conservatives a double-digit lead over Labour, and May is gambling that an election will deliver her a personal mandate from voters and produce a bigger Conservative majority.
That was 1983 during the Margaret Thatcher era, and it's deja-vu for Britain's Labour Party more than three decades later under another Conservative premier, Theresa May.
Downing Street knows they will take a certain amount of flak for the decision not to play ball, and the opposition parties are of course relishing every opportunity to say that the PM is too frightened to defend her record.
Speaking after a meeting of Labour's governing National Executive Committee, Mr Corbyn said: "There will be no coalition deal with the SNP and a Labour government".
Tory sources say she is set to include specific pledges to overcome opposition within her party and in the Lords.
However, the academic argued that it won't be an easy win for May because 48 percent of British voters were against Brexit in last June's European Union referendum and they are not likely to change their mind on June 8.