A second Scottish independence referendum should take place in 2020, the SNP 's Westminster leader Ian Blackford has said.

Speaking to Ridge on Sunday on Sky News, Blackford said Labour leader Jeremy Corbyn "has to be" ready for a second independence referendum if he becomes prime minister.

Corbyn earlier told the programme that he would not consider a second independence vote for the first few years.

Blackford said: "I think he (Jeremy Corbyn) has to be (ready) and I'd simply say to Jeremy Corbyn that we have a mandate for an independence referendum already that was won in the 2016 election, the election to the Scottish Parliament that the SNP won.

"And there is an independence majority within that Parliament.

"So I'd simply say to Jeremy and indeed anybody else that may be in 10 Downing Street that they have to respect democracy, and they have to respect the right of the people that live in Scotland to determine their own future.

"We're putting legislation through the Scottish Parliament now that will enable that to take place.

"That referendum should take place in 2020."

On the Prime Minister's renewed Brexit plans, Blackford warned people not to be optimistic about a deal being secured by the end of the week.

He said: "We've made it very clear that there is no such thing as a good Brexit.

"We need to be staying in the European Union and we should certainly be staying in the single market and the customs union which is the least worst option for us.

"Let's see what happens this week - we haven't seen a deal come forward from Boris Johnson the way they've been talking about.

"I think over the next 24 to 48 hours we'll get more clarity on this, but I'd just express a degree of concern to the people expecting we're going to get a deal before the end of this week."

Blackford added that the Government must respect the Benn Act and write a letter asking for an extension if a deal is not agreed to or Parliament has not approved a no-deal Brexit by October 19.

He said: "And what I say to Boris Johnson and to Conservatives is that they must respect the Benn Act.

That Parliament has taken back control and has legislated to make sure that we don't leave on a no-deal basis at the end of October and that is the first priority that we face."

Blackford added that Boris Johnson "is not someone we can trust".

He said: "The SNP have been calling for the last few weeks for a motion of no confidence because quite simply Boris Johnson is not someone we can trust.

"He hasn't given any indication, any clear indication anyway, that he will observe the Benn Act.

"The smartest thing for the Opposition to do is to recognise that responsibility by having a motion of no confidence to get Boris Johnson out of office."

Pushed on whether the SNP would back Corbyn as an interim government leader, Blackford said: "I don't think it's so much about who forms that caretaker administration, but it's about making sure that we work together, that collectively we recognise the responsibilities we have."