What time is the Brexit 'meaningful vote' in Parliament tomorrow, and what will happen if Theresa May's deal is rejected?

After months of negotiations, the Brexit deal was due to be voted upon in order for the United Kingdom's Parliament to approve or reject Theresa May's controversial plan.

However, last month the prime minister dramatically called off the "meaningful vote", in the face of what had been expected to be a significant defeat at the hands of rebel MPs.

Shortly after delaying the vote, the Prime Minister announced that it would instead be held in the week beginning on the 14th January - with a debate in Parliament taking place from the 7th January.

Last week government sources confirmed that the vote would take place on Tuesday 15th January, despite little indication that the deal has gained any support in the past month, with a number of MPs remaining strongly opposed to the deal.

But what does all this mean for the "meaningful vote" exactly, and what will the outcome mean? Here is all you need to know about what it is and the process involved.

What is the "meaningful vote" on Brexit, and how will it work in the House of Commons?

The "meaningful vote" Parliamentarians have on both the Withdrawal Agreement and the outline for the future relationship between Brexit Britain and the European Union was made law under Section 13(1) of the European Union (Withdrawal) Act 2018, which requires the draft deal to be put to both the House of Commons and House of Lords.

If MPs pass it, the deal will have much less of a problem making its way through the House of Lords.

When has the vote been rescheduled for?

The vote was originally expected to take place on Tuesday 11 December at around 7pm. But now the debate has resumed, with the meaningful vote taking place on Tuesday 15th January. Although exact timings are yet to be confirmed, it is expected to take place between 7pm-9pm.

The Prime Minister's official spokesman said that Mrs May would observe the "spirit" of the EU Withdrawal Act, which requires her to make a statement to the Commons "before the end of January 21" if no agreement in principle has been reached with Brussels.

There was confusion at Westminster over whether the January 21 deadline applied, as a withdrawal deal has been reached. But Commons authorities suggested it did not, saying that in principle the ratification vote could take place as late as March 28 - the day before Brexit is scheduled to happen.

Will Parliament vote for or against the deal?

As it stands, the Government appears likely to lose any vote on the current deal. Over 100 Conservative MPs have voiced opposition to it. The DUP and its 10 MPs have made clear they would vote against it. Hardcore Remainers, meanwhile, were planning to vote the deal down in the hope of a second referendum instead.

That means Mrs May would have needed Labour votes to succeed. However, the Labour leadership has been adamant that it opposes the deal and wants a general election. Convincing up to 100 opposition members to rebel and vote with the Government would have been a very tall order.

While defeat seemed certain, the hope had been that it would have been small enough for the Prime Minister to survive and head to Brussels to renegotiate.

However, Downing Street has grown worried that the defeat would be too heavy for Mrs May to carry on after. Instead, the vote has been delayed and Mrs May will try and win concessions from the EU first.

She is unlikely to get anything major from Brussels. The key issue, the Irish backstop, is not open for renegotiation. The demands from the Brexiteers for a time limit or a unilateral exit mechanism would render the backstop incapable of performing its intended job and so the EU will not allow it.

Nor is Brussels willing to reopen the legally-binding Withdrawal Agreement more generally. It fears demands from member states over issues such as fishing and Gibraltar. So all that will be on offer are small tweaks to the non-binding Political Declaration and perhaps a statement from EU lawyers on the backstop not being permanent.

None of which will be big enough to change the minds of most Brexiteer MPs. They might, however, reduce the size of the rebellion and thus make the two vote strategy viable again.

What happens if MPs do not pass it?

The original plan, once it became clear the Government would lose the vote at the first attempt, was to try again a few days later. The expectation was that Mrs May would try and negotiate a few concessions from the EU, while market turmoil would spook MPs and make them think again. Although, with traders being fully aware of the plan and so "pricing it in", the odds of a major shift in the markets looked slim.

While the "renegotiation" will now happen ahead of the vote, Downing Street may still need more than one attempt to get it through Parliament.

In the intervening period between a first and second attempt to pass the deal, Labour would probably try and force a general election. This would be very difficult because of the Fixed Term Parliament Act and would require Conservative MPs to help topple their own government.

If and when that attempt fails, Labour might try and secure a vote for a second referendum. This would still require support from Tory MPs but would likely be easier than forcing a general election. Those efforts were boosted recently by the European Court of Justice ruling that the UK can revoke Article 50 unilaterally.

The ruling removes the risk of Britain either not being allowed back in or having to make hugely unpalatable concessions such as agreeing to join the euro.

In the meantime, there might also be attempts to push the Government towards a softer Plan B, probably along the lines of "Norway Plus". This would mean staying in the single market and the customs union and continuing freedom of movement. It would, however, have an exit mechanism, unlike the Irish backstop, and potentially command a majority in the house. Several Cabinet ministers are rumoured to have been looking at the idea, but Labour continues to say that it is against a Norway-style Brexit.

If and when attempts at a second referendum or Norway-style Brexit fail, Labour MPs would have to seriously consider voting for Mrs May's deal. The alternative would be a no-deal Brexit.