SNP depute leadership hopeful Julie Hepburn has called for calm in the row over the timing of indyref2. The party activist asked members to trust “our First Minister to make the right judgement when the time comes” but added that the campaign to win needed to start right now.

The question of when there should be a second referendum on independence has dominated the contest to replace Angus Robertson.

Hepburn’s rival Chris McEleny, the Inverclyde councillor, has called for a vote in the next 18 months, while the other contender, Economy Secretary Keith Brown, says the poll and campaign cannot start until party members are properly prepared.

Hepburn said independence was “tantalisingly close” in 2014, but that any future campaign should not be a “re-run” of the previous one.

“Simply shouting the same arguments more loudly is not going to convince those who can be persuaded,” she said. “We need to build a renewed case for independence, and start laying those campaign foundations now.

“We don’t need a date in the diary to start this work. It’s vital that we launch a fresh campaign for independence right now if we are to have a chance of winning a second referendum.

“At the heart of these early stages of a renewed campaign must be engaging and listening to those who voted No in 2014. Some people will never be open to the idea of independence, but significant numbers of people who voted No last time are there to be persuaded.”

Hepburn added: “We undoubtedly have a mandate for an independence referendum, and I trust our First Minister to make the right judgement when the time comes and have every confidence our views as SNP members will greatly inform that decision.

“But if we continually focus on the when, then I believe we risk neglecting the more fundamental question of how – how to do we win an independence referendum?

Brown told The National that the SNP are not yet ready to fight and win a campaign on independence.

“We’ve got to be ready before the next referendum is called,” he said. “The party and its organisation have to be ready to campaign in that referendum and that’s the task we face now – getting ready.

He added: “Whenever we go into any campaign what will matter will be our readiness – if we’re not ready, we won’t win and I want to win.”

McEleny said he thought Scotland could not “afford to wait any longer to see if things can get better,” which is why he wanted a “referendum on our independence within the next 18 months”.

On Tuesday, Angus MacNeil became the first SNP MP to publicly back a vote on Scottish independence sooner rather than later.

Last week, his Westminster colleague Pete Wishart said the vote should only be held when there were “optimum conditions for success”.

MSPs gave the Scottish Government a mandate in March last year to formally request from the UK Government the powers to stage a vote, But after the SNP lost 21 seats at the General Election, the First Minister shelved plans, promising to update the country in the autumn of this year.

Ladbrokes yesterday offered odds of 2/1 for the next referendum being before the end 2020 or after 2024, and 6/4 of the vote coming between 2021 and 2023.