The SNP's Westminster leader Ian Blackford has called for Theresa May to resign if she fails to deliver a Brexit vote this week.

Earlier on Tuesday the PM ruled out putting a "meaningful vote" to the Commons this week, but insisted one would be held by March 12.

Reacting to the news, Blackford said: "If as suggested Theresa May does not bring the promised Brexit vote this week she will have failed to deliver what she promised.

"She should do the honourable thing and go, she is incapable of showing leadership. We must extend article 50 this week and remove the cliff edge."

Mrs May also said that Cabinet collective responsibility had not broken down after pro-EU ministers signalled they could support backbench moves to delay withdrawal in order to prevent a no-deal exit from the bloc.

The Prime Minister said because "positive" talks were ongoing with the EU, a meaningful vote would not be held this week.

Speaking on her way to an EU-League of Arab States summit in Sharm el Sheikh, Egypt, she said: "I was in Brussels last week. My team will be back in Brussels again this coming week. They will be returning to Brussels on Tuesday.

"As a result of that we won't bring a meaningful vote to Parliament this week. But we will ensure that that happens by March 12.

"But it is still within our grasp to leave the European Union with a deal on March 29."

Mrs May also said the Government was still in talks with the EU about the Northern Ireland backstop.

She said: "We are still in that negotiation. We are still talking to the EU about various ways in which we can find a resolution to the issue that Parliament raised."

The PM insisted collective Cabinet responsibility had not broken down after the intervention by Amber Rudd, Greg Clark and David Gauke indicating that they could back parliamentary moves to stop a no deal.

She said: "No, collective responsibility has not broken down. "What we have seen around the Cabinet table, in the party, and in the country at large is strong views on the issue of Europe.

"That is not a surprise to anybody.

"We have around the Cabinet table a collective, not just responsibility, but desire, to actually ensure that we leave the European Union with a deal. That's what we're working for and that's what I'm working for."