Boris Johnson faces a new battle in the Commons after his first vote as PM saw him lose to rebel Tories and opposition MPs who object to a no-deal Brexit.
The Commons voted 328 to 301 to take control of the agenda, allowing them to bring a bill requesting a Brexit delay.
The PM is to call for a general election if he is forced to request an extension to the 31 October deadline.
MPs will now vote on the Brexit delay bill. If it passes, the vote on whether to hold an election will follow.
Wednesday in the Commons will also see Chancellor Sajid Javid outline the government's spending plans, with the health service, education and the police expected to fare well.
Speaking late on Tuesday to a packed House of Commons, the prime minister said the MPs' bill would "hand control" of Brexit negotiations to the EU and bring "more dither, more delay, more confusion".
He told MPs he had no choice but to press ahead with efforts to call an October election, adding: "The people of this country will have to choose."
- Live updates: Johnson to face MPs after Brexit defeat
- Kuenssberg: Politics is upside down
- Brexit's big week: Five things we learned on Tuesday
The BBC understands the government intends to hold an election on 15 October, two days before a crucial EU summit in Brussels. This is a day later than the BBC was previously reporting.
Mr Johnson has tabled a motion in Parliament seeking approval for an "early general election" but has not specified a date.
Labour has said the bill taking the no-deal option completely "off the table" needs to be passed before his party would support the call for a general election.
Shadow Brexit Secretary Sir Keir Starmer told BBC Radio 4's Today that Labour wanted a general election but "on its terms not Boris Johnson's terms".
He said the party did not "trust" the PM to hold the election before the Brexit deadline – as he has insisted he will – suggesting Downing Street had "lied" last month when it denied reports that it planned to suspend Parliament.
"We are not shy of a general election but we are not going to be trapped into abandoning control of Parliament or be taken in what Boris Johnson says because we don't trust him."
Under the Fixed Term Parliaments Act, a prime minister must have the backing of at least two-thirds of the UK's 650 MPs before a general election can be called outside of the fixed five-year terms.
Downing Street said the 21 Tory MPs who rebelled in Tuesday's vote would have the whip removed, effectively expelling them from the parliamentary party and meaning they could not stand as Conservative candidates in the election./BBC News