Toni Giugliano suggested it was unrealistic to expect UK ministers to open negotiations on independence on the back of a general election victory, but argued getting agreement to another “gold standard” referendum would “honour democracy”.
Ms Sturgeon vowed to push ahead with her plan to turn the next general election into a de-facto referendum after the Supreme Court ruled the Scottish Parliament does not have the power to legislate for an independence vote without UK agreement. She had wanted to hold another referendum in October next year.
The First Minister said a special party conference would be convened to agree details of the plan. The Conservatives, Labour and the Liberal Democrats have already said they will not treat the election as a single-issue vote.
Addressing the SNP’s annual St Andrew’s Dinner in Glasgow yesterday evening, Ms Sturgeon said the Supreme Court judgment had “galvanised the Yes movement right across Scotland”.
Speaking to The Scotsman, Mr Giugliano, the SNP’s policy development convener, said: “In my mind if we come out of that election with a commitment to a section 30 order [the mechanism that allowed the 2014 vote], then that's exactly where we want to be, because at the end of the day it remains the gold standard.
"It's not the only route, as the FM [First Minister] said. It's not the only democratic route. But I think if we come out of that election and negotiations with a section 30 order, then I think that that would honour democracy in Scotland and it would put the UK in a much better light on the international stage."
He added: "If the UK Government wants to come to the table and start negotiations on independence on the back of a de-facto [referendum], then I'd be delighted. But I'm also a realist and I think that any advance on bringing the UK Government to a table is a win for Scotland."
Mr Giugliano said: "There are some who see the de-facto referendum as 'oh well, that will mean that we achieve independence there and then'. The de-facto referendum in many ways is a tactic for us to be able to pursue independence, to keep it on the agenda, and to, at the very best, begin negotiations with the UK Government.”
He said a hung parliament could leave the SNP as “king-makers”. Mr Giugliano said: "This is ultimately about taking the people of Scotland with us and giving them a platform and a voice to be able to begin those negotiations. Or indeed, to drag the Prime Minister to a table where we can compromise on a section 30 order."
Mr Giugliano insisted there was "no easy route", adding: "Of course it's risky. It should be risky. We've been in Government for 15 years. The reason why we're here is not to perpetually be in Government – the reason why we're here is to deliver independence for Scotland.”
He argued the Conservatives had "ironically" set the blueprint for running an election on a single issue. "What have the Tories been doing exactly since 2014?” he said. “They have run elections in Scotland on a single issue. I couldn't tell you what any Conservative Party policy in Scotland is beyond 'stop indyref2'."
Elsewhere, Mr Giugliano said he had been “clear from the outset that I want us to co-operate really strongly with the likes of the Scottish Greens on the campaign as a whole”.
He added: "The SNP might be the largest party, but it's not the only component of the Yes movement, and I think it's important for us to work with the likes of the Scottish Greens. In terms of candidates and in terms of wording, yes, I think we need to do that.”
But asked if this included Alex Salmond’s Alba Party, he said: "What I would say is that I want us to work with political parties that will help us win the next referendum."
Asked about co-ordinating with the SNP, a spokesman for the Scottish Greens said every vote for the party “will be regarded as a clear and unambiguous vote for independence”, adding: "It is for each party to decide their own strategy for the election campaign. The Scottish Greens will lay out a positive and distinct vision for a fairer, greener and independent Scotland and will stand on our own manifesto, as we have in previous elections.”