MP Joanna Cherry’s call for Holyrood to legislate to hold an independence referendum if Boris Johnson continues to block an agreed vote with the Scottish Government has been rejected by her Westminster colleague Alyn Smith as a “gesture”.

Cherry, the SNP’s justice and home affairs spokeswoman in the ­Commons, argued on Friday if that if the Prime Minister continued to veto a new plebiscite should there be a pro independence majority in ­Edinburgh after the May election, then the ­Scottish Parliament should hold one.

She referred to comments made by Nicola Sturgeon in her Brexit Day speech in January when she drew attention to the possibility with the First Minister warning it could “move us forward – but equally it could set us back”.

But Cherry, a QC, disagreed. “It is my view that if the pro-independence referendum parties obtain a ­majority at the Scottish election next year and the PM refuses to come to the table to negotiate a second Edinburgh Agreement, the avenue which the FM contemplated earlier this year should be pursued,” she said, delivering the Wales Centre for Government’s ­annual lecture.

READ MORE: Joanna Cherry: Holyrood should hold indyref2 if Boris Johnson blocks new vote​

She insisted that whatever the outcome, the independence cause would not be damaged and underlined the political context in which any future referendum bid was made.

“It would be for the courts to decide whether the bill passed was within the competence of the Scottish Parliament and, thus, whether the referendum so authorised could proceed ... The case would undoubtedly end up in the UK Supreme Court,” she said.

“If they found the bill to be within competence, then we would have a lawful referendum. And one which would be hard for unionists to ­boycott. If we lost then I do not ­believe we would be any further back than the stalemate that will ensue if Boris Johnson digs his heels in.”

Asked on BBC Radio Four’s Any Questions, broadcast yesterday and on Friday, whether he agreed with Cherry about Holyrood holding an independence referendum if the PM continued to block a new vote, Smith, the SNP foreign affairs spokesman in Westminster, made clear he did not.

He said: “No I don’t. I don’t believe in gestures like that. I think we’ve seen in Catalonia where that leads to. I am here to defend party policy. The party’s policy is we want an agreed referendum with the UK as we did in 2014.”

Pressed that the Scottish Government “wasn’t going to get one” as Johnson had said he won’t agree to one, Smith added: “That position is utterly unsustainable in the eyes of the people of Scotland.

“And every time he does say no we go up in the polls so that is neither democratic or sustainable and that is a political argument.”

He added: “We are a constitutional party we want to join the international legal order as an independent state and that needs to be legitimate in the eyes of the people of Scotland and the international community. So yes of course there are other things we can look at, there are other things we will look at as things go ­forward.”

It is the latest clash between Smith and Cherry.

Last week he hit out at the SNP Common Weal Group (SNP CWG) for launching a list of candidates running for election to the party’s ruling NEC. The SNP CWG are backing candidates – including Cherry – who signed its manifesto calling for ­greater internal democracy in the party.