MPs are to vote on the Government 's EU Withdrawal Agreement on Friday, but the motion will not count as a third attempt to pass a "meaningful vote" on Theresa May's deal because it will not cover the future relationship with Europe.
Commons Speaker John Bercow cleared the motion for debate, ruling that it complies with parliamentary conventions which bar ministers from asking MPs to vote repeatedly on the same proposals.
If passed by MPs on Friday, the vote would qualify the UK to be granted an automatic delay to May 22 of the formal date of Brexit .
But it would not allow Parliament to go ahead and ratify the withdrawal package, as Brexit legislation allows this only after the passage of a "meaningful vote" on both the Withdrawal Agreement and a Political Declaration on the future relationship.
Labour will not back the motion, shadow Commons leader Valerie Vaz has said, as she claimed the Government was trying to "break the law".
She said: "The Prime Minister said on January 14 there was 'absolute clarity on the explicit linkage between the Withdrawal Agreement and the Political Declaration' and she added 'the link between the two documents mean the commitments of one cannot be banked without the commitments of the other - the EU has been clear that they come as a package'.
"The Prime Minister was right then, it seems that she is wrong now. That is why we on this side will not be supporting the motion."
"We are now presented with a motion that breaks that link, on the face of it breaks the law, breaks the European Union withdrawal law."
Moving the motion to enable the debate to take place on March 29 - which was initially stated as Brexit day - the Leader of the Commons Andrea Leadsom urged MPs to back the deal "so that we can leave the EU in an orderly way that gives businesses and people the certainty that they need".
Leadsom said: "Tomorrow's motion gives Parliament the opportunity to secure that extension.
"I think we can all agree that we don't want to be in the situation of asking for another extension and facing the potential requirement of participating in European Parliament elections.
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Labour former minister Chris Bryant said: "So far as I understand it the Government, if the motion were carried tomorrow, would not be able to ratify the Withdrawal Agreement treaty."
Leadsom replied: "What it would mean is that the Withdrawal Agreement bill would then be before this House."
Justice minister Rory Stewart urged Labour to back the motion, telling the BBC: "Logically the people that should have no problem with this at all are Labour ."
He added: "They are going to have many, many other opportunities to veto the Political Declaration, future relationship, if they want to.
"This is just the first stage in the vote."
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In a series of tweets, shadow Brexit secretary Keir Starmer said: "There are four key reasons why you cannot separate the Withdrawal Agreement from the Political Declaration.
"First, the Article 50 process explicitly states that the EU and member state must negotiate an agreement 'setting out the arrangements for its withdrawal, taking account of the framework for its future relationship with the Union'.
"Second, in their letter of 14 January Presidents Tusk and Juncker said: 'As for the link between the Withdrawal Agreement and the Political Declaration....it can be made clear that these two documents, while being of a different nature, are part of the same negotiated package'.
"Third, the PM has said the two documents should be treated as one. On 14 January she said "the link between [the two documents] means that the commitments of one cannot be banked without the commitments of the other. The EU has been clear that they come as a package.
"Fourth, following the PM's commitment yesterday to resign before the next phase of negotiations begin, if the withdrawal agreement passes without a credible plan for what happens next then Brexit is going to be determined by the outcome of the next Tory leadership contest.
"What the Government is doing is not in the national interest and that's why we will not support it tomorrow."
