NICOLA Sturgeon faces a "robust discussion" with members of the SNP's ruling body this week on how to move forward with her de facto referendum plan to achieve independence.

The party's national executive committee (NEC) will meet on Saturday to flesh out preliminary details of its new strategy.

It follows the Supreme Court's ruling that Holyrood cannot hold a referendum without Westminster's agreement.

The ruling scuppered the party' plan to use devolved powers to hold Indyref2 after successive Prime Ministers have refused to consent to a new vote, meaning the First Minister has had to move onto her fall back plan, first set out to MSPs in June, of using the next general election, due in 2024, as a de facto independence referendum.

Under her plan if more than half the electorate vote for pro-independence parties in the next general election she would begin independence negotiations with whoever is Prime Minister at the time.

However, there is internal disquiet over Ms Sturgeon’s proposal, even from party loyalists.

There is concern among some over achieving more than 50 per cent of votes as Labour seek to make the election about ousting Rishi Sunak and the Conservatives from power and putting Keir Starmer in Number Ten.

Critics have also pointed out the general election franchise, unlike that for Holyrood elections, excludes 16 and 17 year olds and EU nationals who don't have UK citizenship. Both are among the demographic groups more likely to back independence. Some in the SNP also fear new UK laws requiring voters to bring photo ID to polling stations for Westminster elections could also put the independence side at a disadvantage by depressing turnout.

In 2015 when the SNP won a record 56 out of 59 seats at the general election the party took 50% of votes. With the Greens the total votes for the two independence supporting parties came to 51.3%.

But it is also unclear how, even if the SNP and other independence supporting parties win more than 50% of the popular vote, how independence would be achieved if the new UK Government would not negotiate. And if the Yes side lost, would that mean the question of independence is settled?

Stewart McDonald, the Glasgow South MP, said at the weekend that it would be a “mistake” to focus only on settling the independence question as quickly as possible.

And earlier this month SNP activist Marcus Carlaw described it "as a high risk gamble with little prospect of delivering independence".

Now the NEC is to weigh up the arguments and criticisms as it discusses whether the next general election should be used as a "de facto" referendum, as the First Minister has said or whether instead to use the next Scottish Parliament election in 2026 or to call an earlier Holyrood vote to be used in this manner.

A further possibility being discussed by senior figures, and which is also expected to be debated at the NEC meeting, is whether to use the general election to campaign on the issue of "Scotland's right to choose how it is governed" as a means of putting pressure on a new UK Government to agree to a referendum following the process which preceded the 2014 vote.

The NEC is expected to consider these options in what The Herald was told will be a "robust" discussion on Saturday when its members draw up a draft resolution on the de facto referendum for the party's special conference in March.

It is understood the meeting will also consider whether votes in the general election for the pro-independence Scottish Greens and/or Alba Party would count towards a victory for the independence side or whether only SNP votes should be taken into account.

A provisional agenda for the special conference will be issued on January 20, with members given four weeks to submit amendments to the resolution on the de facto referendum. The final agenda will be issued on February 24 before the conference takes place on March 19.

"The NEC will meet on Saturday and decide the best way forward for Scotland to become an independent country, whether it's a general election. It will be defining what the de facto referendum actually means," a party source told The Herald.

"In the public debate there are a lot of people arguing for a Westminster election, some are arguing for a Holyrood election and there are some people, such as the MP Stewart McDonald, that maybe this isn't the way to go. There are all sorts of views."

The source added: "Branches and members will be able to put forward any variations, so we could after the amendment period end up with a series of options with votes on at conference. The NEC resolution is only the very start of the process.

"The NEC and party members will give consideration to all of the options. One of the options is Westminster, another one of the options is a Holyrood election, even there it could be a Holyrood election at the next [scheduled] election or it could be an earlier Holyrood election...There is also the option that has been floated that you could run the general election as 'a Scotland's right to choose' election to get over 50 per cent of the vote to demand a Section 30 order.

"This needs to play out. I think the NEC will have a fairly robust discussion at the weekend."

The source went on to say some of the criticism to date of the de facto referendum plan was premature as the details about it had not been published.

"To be fair to the FM she has not had the chance to put forward the actual detail of the plan and people are surmissing on something which has not been published yet.

"So let's wait for the actual proposal to be published and then may be we can tear it apart," said the insider.

Another party source added: "I am sure it is not very popular. Trying to use a Westminster election isn’t particularly clever, at least not if you set the bar as 50 per cent of the votes rather than a majority of MPs.

"All sorts of disadvantages (no EU voters, under 18s, new Tory voter suppression ID).

"However, the main snag is the media will completely ignore it as it will be all about Sunak v Starmer and what happens in England. So half the voters probably would not even realise it was supposed to be a plebiscite."

However, today some commentators outwith the party, supported the general election/ de facto plan.

Dr Kirsty Hughes, founder of the former think tank, the Scottish Centre on European Relations, commented on the possible routes forward.

Responding to an earlier edition of this article, she tweeted: "Running general election on 'right to choose' would look more like running away; postponing to 2026 wouldn't exactly suggest confidence & dynamism either (& likely to be under a different FM). Given the state of the UK, de facto referendum at general election looks strongest bet."

Growing unease within the SNP over the First Minister's plan to use the next general election as a de facto independence referendum follows a rebellion among SNP MSPs over Scottish Government reforms to the Gender Recognition Act, the standing down of Ian Blackford, a close ally of Ms Sturgeon, as the SNP's leader at Westminster and the defeat of Alison Thewliss, believed to be the FM's preferred candidate, in the contest to succeed him.  

The SNP has been approached for comment.