MPs belonging to the Scottish National Party could block a UK Government plan for Brexit unless it contained "special arrangements" for Scotland, a deputy leadership candidate has said.
Tommy Sheppard, MP for Edinburgh East, said that the party's 56 MPs could vote down proposals that don't reflect the fact that the majority of Scots voted to Remain in the European Union.
He made the comment as he launched his campaign for the deputy leader post vacated by Stewart Hosie, with a pitch to overhaul the party in preparation for a second independence referendum.
First Minister Nicola Sturgeon has already said that the option of a second independence referendum must be on the table to protect Scotland's interests.
Mr Sheppard was asked by a member of the audience what would happen if the Prime Minister blocked a second independence referendum and Scotland was taken out of the EU.
He said: "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 added that he would argue that "unless the Brexit plan contains special arrangements for Scotland to allow us to have a different relationship with the EU - keeping our European passports while our neighbours in England and Wales lose theirs" he would vote down any Brexit plans.
"We are not completely powerless in this game, we do have some influence," he said.