MPs are to vote again on Brexit on Friday, but the debate will not amount to a third attempt to pass a "meaningful vote" on Theresa May's EU withdrawal package.

Leader of the House Andrea Leadsom told MPs that the House of Commons will hold an unscheduled sitting on March 29 - originally slated to be Brexit Day - to consider a motion on EU withdrawal.

Leadsom appeared to indicate that MPs could be asked to approve the Withdrawal Agreement reached last November, but not the Political Declaration setting out plans for a future trade and security relationship with the EU.

Passing the Withdrawal Agreement alone would allow the UK to qualify for an extension in Brexit talks to May 22 under the terms set down by the European Council last week.

But it would not fulfil the requirements of last year's EU Withdrawal Act, which stipulates that both elements must be approved by MPs to pass the "meaningful vote" allowing the deal to be ratified.

Asked by Labour MP Chris Bryant whether the two parts of the Brexit package were being separated in this way, Leadsom replied: "What a motion that comes forward tomorrow must do is is it must enable us to meet the Council conclusions which say that any unilateral commitment, statement or other act should be compatible with the letter and the spirit of the Withdrawal Agreement."

No information was being made available on the wording of the motion to be tabled later on Thursday, but a Downing Street source said it would not be the third "meaningful vote" under the terms of the Act - known in Westminster as MV3.

The Prime Minister must secure Commons approval for her deal by 11pm on Friday for the UK to be granted an automatic delay to May 22 of the date on which it leaves the EU.

Friday's debate is dependent on a business motion being moved and passed by the House later on Thursday, and on Speaker John Bercow deeming that the Government's proposal is in line with parliamentary rules which ban the same motion being repeatedly tabled.

Downing Street has previously indicated that a third "meaningful vote" would only be attempted if the Prime Minister felt there was a credible chance of success, after its defeat by 230 votes in January and 149 in March.

The Democratic Unionist Party said on Thursday that its opposition to the Withdrawal Agreement remained unchanged.

The National: Sir Keir StarmerSir Keir Starmer

Shadow Brexit secretary Sir Keir Starmer said Labour would not accept any attempt to separate the Withdrawal Agreement from the Political Declaration, which he warned would result in "the blindest of blindfold Brexits".

Following May's announcement on Wednesday that she will stand down before negotiations on the future relationship begin, a failure to seal the Political Declaration could leave the UK facing "a Boris Johnson Brexit, a Jacob Rees-Mogg Brexit or a Michael Gove Brexit", he warned.

"We would be leaving the EU, but with absolutely no idea where we are heading," Sir Keir told a conference of the British Chambers of Commerce (BCC). "That cannot be acceptable and Labour will not vote for it."

Leadsom told MPs that talks were ongoing to ensure Friday's motion complies with Bercow's ruling that MPs must be offered a proposal which is substantially different from earlier versions.

She said: "The European Council has agreed to an extension until May 22 provided the Withdrawal Agreement is approved by the House of Commons this week.

"It's crucial we make every effort to give effect to that and to allow the House to debate this important issue.

"We do not want to be in a situation of asking for another extension and, of course, for the requirement to undertake European Parliament elections."

Talks were continuing on Thursday to try to win round the Conservatives' DUP allies, who indicated on Wednesday that they were not willing to back the deal because of its controversial "backstop" provisions for the Irish border. However, the PM's spokesman had no information about May getting personally involved in meetings with the Northern Irish party.

The Prime Minister's dramatic promise to resign if her deal goes through has convinced some key Tory Brexiteers finally to back her, raising hopes in Downing Street of a breakthrough.

But with the DUP and a hardcore of Tory Eurosceptics holding out against the deal, the Government appears not to have the numbers in the Commons to be sure of victory.

The support of the DUP had been seen as crucial, both in making up the numbers for the vote and in winning over Tory waverers.

Rees-Mogg, leader of the pro-Brexit European Research Group (ERG) who is now supporting the deal, suggested a way could still be found to get the DUP on board.

"I'm in favour of the deal and I hope the DUP will come over to the deal but we'll have to wait and see what they do," he said.

May's effective deputy David Lidington pleaded with MPs to back the Brexit deal.

Speaking at the BCC conference, he recognised "real frustration" in the business community over the uncertainty caused by Brexit.

"From the Prime Minister down, the Government is doing all it can to secure a Brexit that does follow the result of the 2016 referendum but does so in a way that protects jobs and economic growth," he said.

Lidington acknowledged that a "chaotic, disorganised Brexit without an agreed deal is something we should not be seeking to have".