An SNP politician was allegedly pinned to the bar of a Fife pub during an argument about the independence referendum.
Both Yes and No representatives have condemned the attack on Kirkcaldy MSP David Torrance, which has sparked a police hunt.
It is understood he was in the town’s Novar Bar with his partner when a man approached them and conversation turned to the referendum.
The man allegedly then lifted the MSP by the throat and pinned him to the bar before various members of staff and a member of the public pulled him off.
The incident was then reported to the police.
A spokesperson for Mr Torrance said: “This sort of thuggish behaviour is clearly completely unacceptable in any situation.
“The Yes campaign has made it clear that everyone must behave, and it is high time the No campaign did likewise.
“The people of Scotland are entitled to a positive debate and a free flow of discussion, which we believe best serves the interests of achieving a Yes vote in September.”
A police spokeswoman said: “We are following a positive line of inquiry and inquiries are ongoing.”
The SNP placed the alleged assault in the context of “abusive” behaviour in the referendum campaign.
Much has been made of online threats being made against figures who have expressed support for both independence and the union.
Linda Fabiani MSP said: “Abuse of people has absolutely no part to play in the referendum debate. It doesn’t matter whether those doing it support Yes or No.
“Indeed, a recent poll showed that Yes supporters are nearly three times as likely as No supporters to be on the receiving end of online abuse or threats, and it is all to be condemned.”
A Better Together spokesman said: “Abuse of any kind is absolutely unacceptable and should not happen.”