She has also played up the strength of the economy, which has so far defied predictions of a slowdown - a key campaign theme that her Conservative Party will use to try to undermine Labour in the election. Osborne, who has five other jobs as well as a large family fortune, gave the scoop to the Evening Standard, where he is the new editor, although he missed the deadline for the print edition.
The prime minister urged voters to give her "the mandate to speak for Britain and to deliver for Britain".
May says politicians should "put our fate in the hands of the people and then let the people decide".
At least 434 votes were needed in order to approve the election. It needs support from two-thirds of members of Parliament to pass.
MPs have voted in the House of Commons Wednesday and voted for general election on 8 June.
The remaining 27 European Union countries will be asked to endorse Tusk's guidelines at a summit on April 29.
A European Commission spokesman said the "real political" negotiations on Brexit will start after the election.
"Yesterday she changed her mind, not for the good of the country, but for reasons of simple party advantage", Nicola Sturgeon, leader of the Scottish National Party, told supporters at a rally.
The latest poll comes after ComRes and ICM gave the Conservatives a 21 point lead, suggesting Theresa May could win a triple-digit majority at the general election on 8 June.
One broadcaster, ITV, said it planned to hold a debate with or without the prime minister. Demmer said Wednesday: "The German government assumes that the negotiations can be continued without disruption".
United Kingdom commentators say the relentless political logic of an early election, that the Conservatives are expected to win well, has proved too tempting.
During the weekly session of Prime Minister's Questions in the House of Commons, May accused opposition MPs of trying to thwart the Brexit process.
ITV has confirmed it will host a leaders' debate during the general election campaign, despite Theresa May's insistence that she will not take part. "I hope the former will be the case".
The First Minister said the SNP was fighting to win the election in Scotland, but did not need to secure a majority of the vote to keep up the pressure for a second independence referendum. He added: "If it isn't a triumphant success, it will be to some extent a personal failure".
Britain's prime minister has defended her decision to seek a snap election.
If she can extend her parliamentary majority, May will be able to silence critics who have opposed her own policies, not just on Brexit but also tax and education.
Ms May formally notified the European Union on March 29 of Britain's intention to leave, and said she was confident of reaching a deal on the terms of withdrawal in the two years available. "And as we look to the future, the Government has the right plan for negotiating our new relationship with Europe", May said.