Labour will try to rewrite the Government's Brexit legislation to prevent the UK leaving the European Union without a deal, if Parliament rejects the final withdrawal bill.
Shadow Brexit secretary Sir Keir Starmer will use a speech on Monday to try to recruit a coalition of peers and MPs to reject the "take it or leave it" approach on offer from ministers, which would see a vote against the final agreement interpreted as a decision to back a "no deal" Brexit.
Sir Keir will say at the speech in Birmingham that Labour's approach will "bring back control" over Brexit to Parliament.
"If Parliament rejects the Prime Minister's deal that cannot give licence to her - or the extreme Brexiteers in her party - to allow the UK to crash out without an agreement.
"That would be the worst of all possible worlds."
In the speech, he will say: "That is why in the coming days - and working with others in the Lords and the Commons - Labour will ensure that an amendment is tabled to the EU Withdrawal Bill to strengthen the terms of Parliament's meaningful vote."
He will add: "Our amendment would make it clear that, should the Prime Minister's deal be defeated, it must be for Parliament to say what happens next, not the executive."
The measure will be considered as part of the debate on the European Union (Withdrawal) Bill going through Parliament.
Labour's position on Brexit has come under scrutiny following Owen Smith's dismissal from the shadow cabinet after calling for a second referendum.
The party has not definitively ruled out calling for a second public vote - although deputy leader Tom Watson said it was "highly unlikely" that Labour would call for another referendum.