Colin Fox, leader of the Scottish Socialist Party (SSP), said any potential indyref2 should only be called when there was clear evidence the pro-Union camp could not win again.
The intervention by the former Lothians MSP goes against the grain of thinking among many other pro-independence veterans of the 2014 referendum.
Dennis Canavan, former chairman of the official Yes campaign, Scottish Greens co-leader Patrick Harvie, and senior SNP councillor Chris McEleny have all called in recent weeks for Nicola Sturgeon to set a date for another referendum this year.
The First Minister said last week she understood “the impatience of people who, like me, believe absolutely that the best future for Scotland is to be independent” and would clarify her position after the Holyrood Easter recess.
But Fox warned that rushing into another constitutional vote risked moving independence off the agenda for a generation, pointing to the example of Quebec, where separatists were narrowly defeated in a second referendum in 1995.
In an interview with Scotland on Sunday, he claimed Yes campaigners “should not underestimate” the UK state.
“The debate on the timing of another vote seems confused,” said Fox. “When do you have another independence referendum? Surely the answer is when you have a chance of winning one.
“All the polls show Yes is well behind. The argument for having a second referendum should come after having made a better case for independence so far.
“I’m not one of these people who wants a vote straight away. You should call it when we are ahead in the polls and build up a head of steam from then.
“We are taking on the British state. Too many people underestimate our enemy. Whatever else you want to say about the weakness of the socialist movement in Scotland, it has never underestimated the British ruling class.
“There is no sign of Yes winning a second referendum just now so therefore we must be patient.”
The SSP was one of the political parties, alongside the Scottish Greens and the SNP, to form part of the official Yes campaign in 2014.
Achieving unity among the various pro-independence factions ahead of the referendum, particularly those on the left, was a priority for Yes strategists.
But Fox has warned that coalition may be fractured in any future plebiscite if the SNP pursues a more pragmatic economic message.
Many on the left, including the SSP, have been vocal critics of the 2018 economic report produced by the Growth Commission, led by former SNP MSP Andrew Wilson.
Wilson’s report called for an independent Scotland to continue to use the pound and only move to a new Scottish currency if a number of economic tests are met.
“My conclusion is the SNP’s argument is based on the idea that somehow the working class backed independence but the middle class didn’t,” said Fox. “But my view is the Yes movement did not win a majority of the working class in 2014. Not when areas like Fife, Renfrewshire and Invercyde returned majority No votes.
“If a future Yes campaign had the Growth Commission at its centre, would the left rally round it? The clear answer is no. We would not touch it with a bargepole.
“It’s been clear since it was published that it is a complete non-starter.”