A candidate in the race to become the next depute leader of the SNP has suggested his party's MPs could block any UK Government plan to exit the EU unless it contained "special arrangements" for Scotland.

Edinburgh East MP Tommy Sheppard said the party's MPs could vote down any proposal that did not reflect the fact that 62 per cent of Scots voted to Remain in June's referendum:

"Theresa May can serve Article 50 without going to the House of Commons but she needs to get the Brexit plan for what happens next through the House of Commons and there isn't a majority for Brexit in the House of Commons, which she knows full well.

"So our votes, our 56 votes in the House of Commons are going to be quite critical to her getting something through.”

He also took a swipe at his rival for the post, claiming MP Angus Robertson would be double-jobbing if he won the election. Sheppard said Robertson, who leads the party at Westminster, is “already” part of the leadership, and claimed: “This party is not so short of talent that we need people to double up on jobs.”

Sheppard, who is making a direct appeal to the tens of thousands of new SNP members, also called for sweeping changes to party structures he said are rooted in the last century.

The internal contest will see Sheppard, his boss Robertson, councillor Chris McEleny and MEP Alyn Smith vie to replace Stewart Hosie as Nicola Surgeon’s number two.

Party sources believe Robertson is the favourite to win, but Sheppard, a more populist figure, could push him close.

At his campaign launch at the Centre for Contemporary Arts in Glasgow yesterday, Sheppard took aim at his main rival’s weak point, namely that he already has a time-consuming job.

Robertson leads the 54-strong SNP group at Westminster, takes part at Prime Minister’s Questions every week and is a fixture on the UK media scene.

Sheppard said: “I am standing in this election because I want to try and bring a new perspective to the leadership team within our party. But we have a fantastic leadership team already.

“In fact, some of my colleagues in this contest already play leadership roles within our party. This party is not so short of talent that we need people to double up on jobs. I want to expand our leadership, not stretch it.”

Answering a question from a member of the audience, he also said: “Some of the press have speculated that the favourite in this contest is Angus Robertson, our Westminster leader. Let me say I have 100 per cent support for Angus Robertson in the job that he is doing. But this is a different job. This is not the same job. This is a job which is about getting our party match fit for independence. And because I am a backbench MP, I have time that I can devote to that, and make sure that that job is done properly."

He added: “Angus, for my mind, is already part of the SNP leadership team.”

Anne McLaughlin, the Glasgow Provan MP who introduced Sheppard, also said: “Although everyone is capable, it is about having the time to focus on the role of deputy leader.”

In his pitch, Sheppard stressed that empowering new SNP members was critical if independence was to be achieved: “It is impossible to run an organisation with 120,000 members on the same rule book that we had for 20,000. We need an organisational upgrade.”

He added: “I am concerned about the people who would like to get involved in a political party, but because of the way we organise on the ground, feel that they are not able to, feel that they are left out.”

Sheppard also warned: “If we don’t find ways to bring our mass membership with us in the challenges that lie ahead, then we may find ourselves falter and stumble.”

In a criticism of the SNP’s centralised policy making structure, he said: “I think the days of 200 branches sending 200 resolutions to a conference arrangements committee that then rules 90 per cent of them out of order are gone. I think that is very last century.”

The MP said internal reform was important as an independence referendum could be held “possibly within the next two or three years.”

He also said his past as a senior figure in Scottish Labour – he was deputy general secretary in the 1990s – could be helpful: “Because I have trodden that path myself [from Labour to SNP], I know how to encourage others to make that journey too.”

A spokesperson for Robertson said: "If elected, Angus will continue to lead the Westminster group as well as being the depute leader of the SNP. Our leadership team already works joint roles – Nicola Sturgeon is our First Minister and party leader. She has shown the real leadership whilst Labour and others have none. Angus already has a good working relationship with Nicola, and it is through that relationship that as depute leader, Angus can ensure that his manifesto for empowering the grassroots on our way to Independence is realised."