'The five-week suspension of Parliament will begin later, after MPs are expected to again reject government calls for a snap election.
Opposition MPs confirmed they would not back the push for a 15 October poll, insisting a law blocking a no-deal Brexit must be implemented first.
Ministers have said they will "test" what the law - expected to get final approval on Monday - requires of them.
Boris Johnson has been warned he could face legal action for flouting it.
The government has described the law - which would force the PM to seek a Brexit delay if MPs have not approved a new deal, or no deal, by 19 October - as "lousy".
BBC political editor Laura Kuenssberg said although No 10 insisted it was not looking to break the law, efforts were under way to examine ways of getting around it.
Two applications have been made to hold emergency debates in Parliament later.
Labour leader Jeremy Corbyn has requested a debate around the rule of law.
The second application is being made by Dominic Grieve - who lost the Conservative whip last week for voting to block a no-deal Brexit - but it is not clear what the subject will be.
Downing Street confirmed that the expected prorogation - or suspension - of Parliament until 14 October would begin at the end of Monday's sitting.
It means MPs will not get another chance to vote for an early election until after then, meaning a poll would not be possible until late November at the earliest.'
Read more: Brexit: Parliament suspension to go ahead later
