NICOLA Sturgeon should be ready to “step aside” as SNP leader and make way for someone with greater “intellectual capability”, the party’s former deputy leader has said.

Jim Sillars criticised the First Minister’s “helter skelter” push for a second referendum and suggested it was only the lack of a decent replacement that kept her in post.

If someone more qualified came forward, she should go, he said.

He told BBC Sunday Politics Scotland. “Suppose Nicola was knocked over by a bus... where are the candidates of the necessary stature to take over the leadership of the SNP?

“So she’s what we’ve got at the present time. I would like to see her improve.”

When it was put to him that he was damning her with faint praise, Mr Sillars replied: “At my age I can talk honestly. If there was someone better around who had the intellectual capability to understand that you’ve got to analyse things first before you take a decision, yes, I think she should step aside.

“But there’s no one there at the moment. So we’ve got Nicola and I hope Nicola improves.”

He added: We lost seats at Westminster because the day after the [EU] referendum she went helter-skelter for a second referendum which everyone knew we would lose and most people didn’t want.”

Mr Sillars, a former Govan MP who was deputy leader to Alex Salmond in the early 1990s, has been a frequent critic of his party in recent years.

A Leave voter, he has been particularly hard on Ms Sturgeon’s enthusiastic support of the EU, and for calling a second independence referendum in March on the back of Brexit.

However he has not suggested Ms Sturgeon might quit until now.

The 80-year-old party veteran also predicted there would be no second independence referendum before the 2021 Holyrood election, and the SNP may not be able to hold one after that - a huge problem it had still not started thinking about.

He said: “You cannot have [a referendum] sensibly until you know exactly what the Brexit deal is in detail, and then take time to assess it, and then take time to formulate an argument for independence.

“Because we’re in a new paradigm. What was in 2014 will no longer be the case when we Brexit. So we have to have a new thinking of the structure which we put to the Scottish people. It’s a huge amount and discussing that needs to be done.”

Asked when the next realistic date for a referendum would be, he agreed it would be after the 2021 election, and warned it might be very difficult after that.

He said: “I think after that you’re talking 2022, 2023 before you actually have the referendum. Of course, we’ve got a problem. If there’s not an independence majority in Holyrood in 2021, how do we extract the agreement from Westminster to hold a referendum? That’s a problem for the whole movement. What do we do?”

He said there was no point going for another vote until the SNP and Yes movement had done its homework, and reflected more deeply on why the No side won in 2014.

He said: “There are reasons why we lost. There has been no post-mortem inside the Yes movement. Why did we lose and what are the answers to it?

“Until we do that, and until we engage in a major educational exercise with the Scottish population, we will lose the second referendum.

“At the moment we’re still stuck around 46 per cent. Why have we not moved up to round about 60? That’s the task that faces the independence movement at the present time and we’re nowhere near even at the starting gate.”

He said the Yes movement of 2014 had “been allowed to die” and should be “resurrected”.

However it should keep its distance from the SNP and not allow the party to become “the gaffer”, as that would tie the movement to the party's electoral prospects.

He said: “If they go down, the movement goes down. What I’m saying to people in the independence movement is we’ve got to sit down and workout the various scenarios.

“What happens if we build the independence movement but the SNP doesn’t have a majority at Holyrood to demand a referendum. How do we cope with that?

“That’s a major intellectual exercise we haven’t even started.

“I don’t have the answer but I do know the questions.”

Mr Sillars also offered “constructive criticism” of Ms Sturgeon’s plan for a not-for-profit publicly-owned energy company to lower customers’ bills, saying it did “not go far enough”.

He said there should be a more ambitious profit-generating public energy corporation instead, involving state involvement in the oil industry, fracking and renewables.

Repeating his call for the SNP to reverse its ban on fracking, he said: "I think the Scottish public didn't really know that there was a major consultation going on, which allowed the green movement to ramp up to 99 per cent against fracking.

"Joe Stalin used to get figures like that as well."