THE SNP will destroy any chance of another cross-party independence campaign if it formally adopts a controversial economic plan at its spring conference, it has been warned.

Colin Fox, co-convener of the Scottish Socialist Party and a former board member of the last Yes campaign, said the Growth Commission would “torpedo” another 2014-style alliance.

He said it reminded him of “something New Labour could have produced”, adding: “I sat on the Yes Scotland Advisory Board and played a constructive, collegiate role. But we will be unable to do so again if the Growth Commission plan is put at the heart of Yes2.”

The Scottish Greens also said the SNP would be "well advised" not to follow the plans.

The attack comes a day after influential members of the SNP warned making the Commission’s ideas into party policy could cause a “crisis in the independence movement”.

READ MORE: Row over SNP's currency plans for an independent Scotland

Chaired by former MSP turned corporate lobbyist Andrew Wilson, the Commission’s blueprint for independence has been severely criticised on the Left of the movement.

It recommended halving the deficit, reining in public spending and keeping the pound for the first decade or after independence to establish market credibility.

The respected Institute of Fiscal Studies said this would be akin to keeping Tory austerity.

Now Finance Secretary Derek Mackay and depute leader Keith Brown have tabled a motion for next month’s SNP conference in Edinburgh accepting the Commission’s proposals.

Although there is an ostensible commitment to creating a new Scottish currency, this would be subject to six annually-assessed economic tests set down by the Commission, which some SNP activists believe are so vague they may never be met.

Mr Mackay admitted on Sunday that an accelerated currency plan would depend on an economic boom after independence. 

READ MORE: SNP currency plan based on economic boom after Yes vote branded 'fantasy'

Mr Fox, who sat on Yes Scotland before the 2014 vote, said the Commission’s ideas meant cuts to public spending, privatisation, further austerity and the continued use of sterling.

He said: “The wider Yes movement will simply not rally behind this recommendation.

“The Scottish Socialist Party will certainly not participate in a Yes campaign based around this free market, right of centre economic prospectus.

“Rather we will work with others to put the case for Independence as meaning profound change, environmental sustainability and social justice for all in our new nation.”

READ MORE: Letters: Plans for a Scottish currency are doomed to fail

He went on: “Wilson offers no material improvement to the often desperate circumstances facing Scotland's working class majority. Yet they are the strongest supporters of Independence precisely because they see progress coming from that route alone.

“Wilson clearly believes Scotland's working class are already 'in the bag' as far as Independence is concerned and concludes the SNP must therefore appeal above all to middle-class, Middle Scotland. His fiscally conservative economics are therefore designed to appeal to Murrayfield and Milngavie, not Motherwell or Methil.

"Pandering to a wealthy elite not only risks losing the 45% support we won in 2014, it makes the task of winning over Scotland’s working class majority impossible.

“And without them Yes cannot triumph.”

Green MSP Patrick Harvie, who also served on Yes Scotland, said: "The SNP’s Growth Commission has been widely criticised, and the wider campaign for independence would be well advised not to base an economic plan on this divisive report.”

Tory MSP Adam Tomkins added: "The SNP’s Growth Commission clearly outlines the years of public spending cuts and massive tax increases that would be necessary in an independent Scotland. Perhaps the Scottish Socialists should rethink their outdated ideology."

LibDem spokesperson Wendy Chamberlain said: “The SNP are repelling independence foot soldiers with moves to endorse their home-made austerity plans.

“The Growth Commission sets out how an independent Scotland would have no choice but to make harsh cuts to public services in order to bring down the deficit. The Scottish Liberal Democrats will oppose these chaotic plans to make our country and people poorer.”

Pamela Nash, chief executive of Scotland in Union, said: “The campaign to leave the UK is tearing itself apart because there simply isn’t a positive economic case for Scottish independence. Whether it’s the SNP, Green or Socialist Party blueprint, families in Scotland would face deeper austerity and steeper tax rises.”

For the SNP, Mr Brown said: “The proposals I have put forward to conference will enable us to build a solid and persuasive platform for independence.

“They give us the powers to fulfil our potential – to build a fairer society, based on shared values of equality and compassion.

“We can reject austerity outright, and protect valued public services like our NHS from the harm of Tory cuts and the damage of Brexit.

“We can pursue a currency policy that’s right for Scotland to maximise our opportunities as a proud, successful European nation in a global economy.

“We can raise our sights by building an independent Scotland that brings about the change we need to face the challenges of tomorrow.”