The founder of the Labour group which backed a Yes vote in the referendum has left the party and is joining the Scottish Socialists.

Allan Grogan said Labour's decision to campaign with the Conservatives and Liberal Democrats in favour of the union had "backfired spectacularly" and "now threatens the party's very existence".

Mr Grogan, who founded the Labour For Independence (LFI) group in the run-up to the referendum, hit out out at his former party and said: "Voters who backed independence in Labour areas in September remain committed to social democratic and socialist change and values which put people before profit. Those values are no longer held by Labour.

"They are held above all by the SSP in this country and I was really impressed by the party's conduct and distinctive role in the Yes Scotland campaign these past two years. I am a socialist and the place for socialists is in Scotland's socialist party. That is why I have decided to join."

Mr Grogan, who will be speaking at the SSP's conference in Edinburgh on Saturday, claimed: "As LFI predicted, Scottish Labour's decision to join the Tories, big business and the Lib Dems in the anti-independence camp has backfired spectacularly and it now threatens the party's very existence."

SSP national spokesman and former MSP Colin Fox said: "I warmly welcome Allan into the SSP and look forward to the positive contribution he will undoubtedly make to the party. I have enjoyed working alongside him in the Yes Scotland coalition for many months."

Scottish Labour leader Johann Lamont has insisted that campaigning with the Conservatives and others in the run-up to the referendum was ''the right thing to do''.

Ms Lamont insisted she was ''absolutely clear'' taking part in the cross-party Better Together campaign had been the correct decision.