LONDON (Reuters) - Britain’s parliament holds a special sitting on Friday to discuss and vote on Brexit, potentially unlocking an extension to May 22 to the country’s exit from the European Union but falling short of the criteria needed to formally ratify the deal.

A pro-Brexit supporter installs Union Jack flags outside the Houses of Parliament, following the Brexit votes the previous evening, in London, Britain, March 28, 2019. REUTERS/Hannah McKay

The government hopes to avoid another heavy defeat on the deal by separating the two elements which make up the exit package: the legally binding Withdrawal Agreement covering the terms of the split and a more vague Political Declaration on the future long-term relationship.

The two documents together have been rejected twice already by parliament in so-called “meaningful votes”. Under British law, the deal cannot be ratified without securing parliament’s approval for both parts.

WHAT IS UP FOR DEBATE ON FRIDAY?

On Friday, the government will ask parliament to debate and vote on the Withdrawal Agreement alone. The full text of the motion up for debate can be found here:

WHAT WILL THE RESULT MEAN?

If government wins the vote, it believes it will have satisfied the conditions set by the EU in order to delay Britain’s exit from the bloc until May 22. These conditions were set out at a European Council summit on March 21.

However, the result will not meet the criteria in British law for the exit package to be formally ratified. The government acknowledges this in its motion.

In order to ratify the Withdrawal Agreement, the government is required to have parliamentary approval for both the Withdrawal Agreement and the political declaration. This would therefore require another separate vote at a future date.

CAN THE GOVERNMENT WIN?

May’s Conservatives do not have a majority in the 650-seat parliament, relying on the 10 lawmakers of Northern Ireland’s Democratic Unionist Party (DUP) to prop up her government.

The Brexit deal was defeated first by a record 230 votes on Jan. 15 and then by 149 votes on March 12.

To overturn the March 12 result, she would need at least 75 lawmakers to change their minds. The DUP and several hardline pro-Brexit Conservatives who object to parts of the Withdrawal Agreement have said they will keep on rejecting the deal.

Therefore success depends on how effectively May can minimise the rebellion in her own party and how many lawmakers from the opposition Labour Party she can win over.

Labour’s Brexit spokesman Keir Starmer said on Thursday the party would not support the Withdrawal Agreement alone as this would leave Britain with the “blindest of blindfold Brexits”.

The government tried on Friday to win over some Labour lawmakers by saying it would have accepted their proposal for parliament to have more influence over the talks on the future relationship with the EU.

But Lisa Nandy, who had indicated that she might back the deal, said May’s decision to quit if the divorce agreement is approved, would undermine any promises the prime minister may make.

WHAT HAPPENS IF THE GOVERNMENT LOSES?

Attorney General Geoffrey Cox said passing the deal on Friday was the only way to ensure Britain locked in a delay to Brexit to May 22. If the deal is rejected, Britain faces a much longer delay, the terms of which would be subject to agreement with the EU, or leaving the bloc on April 12 without a deal.

WHAT HAPPENS NEXT?

Lawmakers are due to take control of parliamentary business on Monday, April 1, when they will likely vote on a narrowed-down list of alternative Brexit plans, designed to discover if there is a majority in parliament for any next step.

This follows a series of votes on Wednesday, in which eight possible options were debated and voted upon, but none won a clear majority.