SCOTTISH Nationalists are set to reopen old divisions by expelling left-wing republicans from the party.
The SNP national executive committee has designated a small activist group, the Scottish Republican Socialist Movement, as a banned organisation.
And any Nationalist who refuses to give up membership of the group now faces being kicked out of the SNP.
The move threatens to undermine the new mood of unity in the SNP since the return of Alex Salmond as leader. His decisive victory in the internal contest in September put an end to much of the inter-faction fighting in the party.
The SRSM has been in existence for the past six years, but the SNP only moved to ban Nationalists from joining it after SNP Midlothian activist Joe Middleton set up a branch in the Lothians.
He said he did not know how many SNP members were in the SRSM. "I’m probably the only one who shouts about it," he said.
SNP officials say membership of the SRSM is incompatible with membership of the SNP because the group is affiliated to the Scottish Socialist Party.
But Mr Middleton pointed out many trade unions were affiliated to the Labour Party, yet SNP members were not banned from joining unions. "You can be a member of SRSM and not be in the SSP," he said. "It’s open to everyone who believes in an independent, republican, socialist Scotland. It’s meant to be a cross-party movement."
Mr Middleton said around 20 supporters had attended meetings in the Lothians since he set up the new branch. He said one reason for establishing the branch was to try to bring back into the SNP some of those who left during John Swinney’s leadership.
"I’m not even bothered about people joining the SRSM," he said. "I’m just hoping people will come along to meetings and discuss the issues."
Mr Middleton - who was threatened with disciplinary action last year after advocating republicanism in an article in the Evening News - said the party’s new stance sent out the wrong message.
"It’s telling people you can be a republican and a socialist in the SNP if you want, but you’re not supposed to shout about it. It’s going to annoy a lot of people. Do they want people to go and join the SSP?"
The SNP usually only bars members from being members of other political parties. But its constitution allows it to "deem" organisations political parties.
In his report to a meeting of the SNP’s national council on Saturday, national secretary Dr Alasdair Allan says "Membership of this organisation [SRSM] has in the past not been viewed as inconsistent with membership of the SNP.
"However, as this organisation is now advertising itself as being affiliated to the Scottish Socialist Party, the NEC has deemed the SRSM to be a political party. Consequently, members are advised that membership of the SRSM will no longer be treated as consistent with membership of the SNP."
Mr Middleton, a member of the SNP for 17 years, indicated he would risk being kicked out of the party rather than accept its latest ruling.
"It’s a point of principle. I’m a republican socialist and I feel I should be able to be in the SRSM. I don’t see why the SNP should be able to force me out," he said.
An SNP spokesman said the issue was an internal party matter and he could not discuss it.