Brexit: MPs to decide on Boris Johnson's deal today - the vote is on a knife edge

Boris Johnson has issued a final rallying call to MPs to back his EU Withdrawal Agreement as rebels plot an amendment that could push Brexit back until the new year to avoid an accidental no-deal.

Number 10 is working desperately to secure a Commons majority for the deal struck by Mr Johnson in Brussels, but a lack of widespread support from opposition parties means the vote is on a knife edge.

Here is what is expected to happen today:

The government has been holding discussions with some Labour MPs in an attempt to get the 320 votes needed, and the prime minister has urged colleagues to back the deal and free the country "from the never-ending Brexit saga".

Writing in The Sun, Mr Johnson insisted his agreement was a "great deal for every part of our country" and an opportunity to bring to an end a "difficult, divisive, painful chapter in our history".

Several members of the cabinet have joined the PM on a newspaper charm offensive, with Michael Gove in The Times warning that "divisions will only grow deeper in our society" if the deal fails to go through.

Home Secretary Priti Patel and Business Secretary Andrea Leadsom, who both voted against Brexit agreements put forward by Theresa May, have sung the praises of the new deal in The Daily Telegraph and Daily Express.

But even if the agreement does get through during a rare Saturday Commons session, it may come with an amendment that could see MPs withhold their support until the Brexit legislation has been safely approved.

If selected by Speaker John Bercow, the amendment proposed by Sir Oliver Letwin would trigger the Benn Act introduced by MPs opposed to a no-deal - and it would compel the PM to request a delay until the end of January.

Sky News' political correspondent Rob Powell reports that the concern among those in favour of the amendment is that hard Brexiteers could purposefully withdraw support later in the month to trigger a no-deal.

Sir Oliver, a former Tory cabinet minister who now sits as an independent, told Sky News that he wanted the deal to succeed, but that an "insurance policy" was needed to keep the UK from "crashing out on 31 October by mistake".

He added: "The amendment is to make sure that we have an insurance policy that means if for some reason something goes wrong when the legislation goes through, then we would have already secured the extension which the Benn Act provides, so we won't crash out of the EU by mistake."

A Number 10 source has also told Sky News if the Letwin amendment passes, the government will pull the vote on the main motion.

Two other amendments have been tabled - one calling for the PM to cancel Brexit and the other calling on him to ask for a delay to hold a general election.

If the vote on Mr Johnson's deal does go ahead, he needs a decent number of opposition MPs to back it as well - especially as he does not having the backing of the Democratic Unionist Party.

There are only 287 Conservative MPs, leaving the PM in need of backing from some of the following:

Sky News analysis suggests the PM is on course for about 316 votes - four short of what he needs.

Number 10 said it has held talks with some Labour MPs and "agreed to make a number of commitments that ensure increased protection of workers' rights and environmental standards".

The government says it is committed to enshrining all existing workers' rights into domestic law, and to report regularly on any future EU measures and whether they will be mirrored in the UK.

Also promised are legally binding environmental targets.

It remains to be seen whether that would be enough to tempt them to defy Labour leader Jeremy Corbyn, who has urged his MPs to vote against the deal.

Sky News' political correspondent Lewis Goodall said there has been a "huge" whipping operation, adding: "Never underestimate the Labour whips."

Today's Common session will coincide with an enormous People's Vote march. Hundreds of thousands of campaigners expected to take to the streets of Westminster to campaign for a second referendum.

Some Liberal Democrat and Labour MPs have suggested they could back a deal if it was put to another public vote, but the government has repeatedly ruled that out.

In his letter published in The Sun, Mr Johnson said there had been enough "false dawns" and too many "deadlines for our departure that have come and gone".

A Downing Street spokesman said: "The public want Brexit done so we can focus on the priorities of the British people, including the NHS and making sure that our children get the best possible education."

Watch a special edition of Kay Burley@Breakfast from 8am on Sky News, with continuing coverage from Westminster throughout the day.