Richard Leonard has been attacked for his “far left” views, with the Tories compiling a list of the stances and causes he has taken up.
Conservatives pointed out the Labour leadership candidate had shared a platform with supporters of the “repressive” Venezuelan regime and had signed a Holyrood motion praising Fidel Castro.
They also said he boycotted Better Together when he was a GMB organiser, preferring to work with Labour’s own anti-independence campaign.
Tory MSP Miles Briggs accused him of siding with the “extreme few”.
Leonard’s campaign said: “This is desperate stuff from a desperate party obviously rattled at the prospect of Richard being elected.”