The SNP's Westminster leader has called on Theresa May to resign during a rowdy session of Prime Minister's Questions.

Ian Blackford told the Prime Minister her government was a "farce" after a confidence vote in her leadership was triggered by Conservative MPs.

The SNP MP also asked if May would table the meaningful vote on her Brexit deal - postponed on Monday - for next week before Parliament breaks for Christmas.

The Prime Minister said her decision to defer the vote was done out of respect for MPs and their concerns over the duration of the Irish backstop.

She faced MPs in the House of Commons for the first time since the meaningful vote, scheduled for Tuesday, was delayed amid fears a heavy defeat on the Brexit deal was likely.

It was announced on Wednesday morning that the threshold of 48 Tory MPs - 15% of the party's total - had written no confidence letters to 1922 committee chairman Graham Brady.

May will therefore face a confidence vote in Westminster on Wednesday evening, between 6pm and 8pm, with the result announced at around 9pm.

If she wins, her party's MPs cannot challenge her again for 12 months, but a defeat would trigger a Tory party leadership contest.

Blackford said the Prime Minister was unable to do her job "because of the Tory civil war" and asked her to confirm if the meaningful vote would be before Christmas.

May replied she would first meet with European leaders, adding: "What matters is that they are in no doubt about the strength of feeling about this issue on the duration of the backstop in this House."

The SNP's Westminster leader said her refusal to confirm the meaningful vote would happen this year was "contemptuous of Parliament".

He continued: "Parliament voted for a meaningful vote, we should be having the vote and it should be happening next week.

"This government is a farce. The Tory party is in chaos. The Prime Minister is a disgrace with her actions.

"The reality is that people across Scotland and the UK are seeing this today.

"Prime Minister, take responsibility, do the right thing, resign."

The Prime Minister answered: "He makes the remarks he does about deferring the vote, but of course it is precisely because I have listened and colleagues in government have listened to the views of people across this House that we are pursuing this issue further with the European Union.

"That is being respectful of the views that have been raised in this House."

Theresa May requires the backing of 158 of the Conservative party's 315 MPs to survive tonight's confidence vote.

So far, more than 170 Tory MPs have said publicly they will vote in support of the Prime Minister - although the ballot this evening is, of course, secret.

Out of Scotland's 13 Conservative MPs, ten of them have stated they will back May, including Scottish Secretary David Mundell.

Berwickshire, Roxburgh and Selkirk MP John Lamont has said he won't comment on how he will vote as he is a member of the 1922 Committee's executive.

Brexiteer MP for Aberdeen South, Ross Thomson, and Moray MP Douglas Ross, have also not said how they will vote.

Scottish Tory leader Ruth Davidson, currently on maternity leave, tweeted her support of the Prime Minister earlier and praised her "cojones of steel".

Jackson Carlaw, who is interim leader in Davidson's stead, told STV News earlier "the only person capable" of delivering Brexit is Theresa May and urged Tory MPs to back her.