MPs have backed a Brexit amendment by West Dorset MP Sir Oliver Letwin that forces Prime Minister Boris Johnson to request a delay to the process.

MPs backed the amendment to the government motion on the Brexit deal by 322 votes to 306.

It means the Prime Minsister will be forced to ask the EU to delay Brexit until all the necessary legislation for a deal has been passed in parliament, to prevent an accidental no-deal.

Boris Johnson was due to face a knife-edge Commons vote on his Brexit deal as Parliament meets on a weekend for the first time in 37 years.

The Prime Minister appealed to MPs from across the political spectrum to back his agreement with Brussels and end a "painful chapter" as the October 31 deadline for withdrawal loomed.

But with once-close allies the Democratic Unionist Party strongly opposed to the deal, Mr Johnson is left needing the backing of Tory MPs from whom he has withdrawn the whip and pro-Brexit Labour MPs to get the deal across the line.

An uphill battle has been made more arduous by West Dorset MP Sir Oliver Letwin the former Tory Cabinet minister who now sits as an independent, whose motion allowing for amendments to the Government's proposals was narrowly passed.

The MP subsequently put forward an amendment that, if selected by Speaker John Bercow and approved by MPs, would withhold approval of the deal unless and until implementing legislation has passed.

Sir Oliver explained his move, stating: "In short, my aim is to ensure that Boris's deal succeeds, but that we have an insurance policy which prevents the UK from crashing out on 31 October by mistake if something goes wrong during the passage of the implementing legislation."

Responding to Sir Oliver's amendment, a Downing St spokesperson said: "The public will be appalled if MPs just vote for delay again. MPs should vote for the new deal so we can get Brexit done on October 31 and the country can move on."

MPs will sit at 9.30am today but the vote is not expected until later this afternoon.

If Parliament does not vote the deal through, Mr Johnson is compelled under the Benn Act to request a further Brexit delay to the end of January - something he has previously refused to countenance.