The SNP has an "open ear" to a potential second referendum on the UK's membership of the European Union, the party's Westminster leader has said.

Ian Blackford said the SNP's priority was making sure Scotland could stay in the single market and customs union, but added the party was "watching developments" over the prospect of another EU vote.

A hard Brexit, he argued, would signal a "clear road map towards a second independence referendum that for me would be the priority".

Blackford said: "Our priority is to make sure that we can stay in the single market and the customs union, we haven't been arguing for a second EU referendum, we're of course watching developments as far as that is concerned.

"We're not in all circumstances diametrically opposed to that, we have an open ear to developments on that front, but for us it's the priority of staying in the single market and the customs union that's most important."

He added: "I think it is clear that if we're out the single market and the customs union there is a massive threat to our economy, to jobs, to prosperity and I would say on that basis that there is a clear road map towards a second independence referendum that for me would be the priority."

The MP for Ross, Skye and Lochaber argued that if the UK Government did not listen to the SNP's "power grab" concerns over its Brexit legislation, then an independence vote could follow and the Scottish Government had a mandate.

He said: "Of course I would make the point that if we cannot get the UK Government to listen on this then ultimately we will be having a discussion with the people of Scotland as to how we best protect our parliament, I would argue that independence is the best way of doing that."

SNP membership he said had "shot up" by 7000 and was "still increasing" following the party's protest at Prime Minister's Questions over the Government's handling of Brexit.

As Theresa May narrowly won another crunch vote on the Government's European Union (Withdrawal) Bill last week, Mr Blackford branded the Prime Minister "very weak", adding "at some point that luck will run out".

The UK Government has previously said the Bill delivers on its pledge to give "significant further powers" to the Scottish Parliament, and it would seek consent unless there are "not normal circumstances applying" - describing Brexit as such an exception.

The Scottish Parliament has not granted a legislative consent motion for the key Brexit legislation.