Theresa May’s plan for a snap general election on 8 June is set to be authorised by MPs later.
The early poll is expected to secure the two-thirds Commons majority it requires to go ahead, with Labour’s Jeremy Corbyn welcoming the PM’s surprise announcement on Tuesday.
Mrs May said that she wanted to secure the backing of the British people for her Brexit negotiations.
She told the Sun newspaper “political game playing” risked hampering talks.
The next general election had been expected in 2020, but the Fixed Term Parliaments Act allows for one to be held earlier if two-thirds of MPs back the move.
A motion to this effect will be put before the Commons on Wednesday afternoon.
The SNP has signalled its MPs will abstain in the vote, but Labour and the Liberal Democrats have welcomed the early election.
Opposition parties have highlighted Mrs May’s U-turn after she had previously insisted she would not be calling an early poll, but Mr Corbyn said it was a chance to get a government that puts “the majority first”.
Opponents also accused Mrs May of ducking out of TV debates during the campaign, after a Downing Street source said she would not be taking part.