A row has broken out after council workers were told to remove "Yes" and "No" campaign stickers from their cars and keep their views on Scottish independence to themselves.
Council bosses warned staff that displaying stickers on their own cars during office hours was strictly forbidden and a breach of conduct – prompting a union leader to step in.
The council said staff were breaking the law if they did not act in a politically neutral way.
One employee, who didn’t want to be named, said he was told to peel the "Yes" stickers off his car, which was parked in a public car park during work hours.
But Inverness Unison official John Gibson urged workers to ignore the "over-zealous" ruling, saying the local authority did not have a legal leg to stand on.
"It’s overkill", he said. "If any Unison member came to me and said ‘I’ve got a ‘Vote Yes’ or a ‘Vote No’ sticker on my car and the council is telling me to remove it’, I would defend their right to put anything they like on their own car – particularly if it is not being used for work.
"Highland Council does not have the power or the authority to do this. It is an infringement of an individual’s right to freedom of expression."
Mr Gibson said SNP members had emailed him, complaining the sticker rule was a step too far. "Where does it stop," said Mr Gibson. "Could this mean that if you are a council employee and you live in a council house you shouldn’t have stickers up in your house?"
The edict was passed down by the local authority’s chief executive Steve Barron. His staff memo says council facilities and resources must not be used to promote the political views of employees.
He said staff and councillors should not wear a campaign badge or display a campaign poster while undertaking council duties in the pre-referendum period.
A council spokesman confirmed: "This will include personal vehicles parked at council offices, schools and other locations."
The guidance places no restriction on staff outside of working hours, except for senior staff in politically restricted posts, and this affects about 50 staff.
However, the employee who raised the complaint does not hold such a post and insisted that his car was parked in a public car park. The council spokesman said there was no record of such an exchange, and said the authority would not necessarily have that kind of information on file.
The ruling comes from the Scottish Independence Referendum Act 2013, which imposes restrictions on the publication of material by public bodies in the 28 days before the referendum.
The act prevents those bodies from publishing material which deals with any issues raised by the referendum question or puts any arguments for or against any outcome.
It states: "The act defines ‘publish’ very widely as meaning ‘make available to the public at large, or any section of the public, in whatever form and by whatever means’.
"A wide range of Scottish Government activity has the potential to be caught by these statutory restrictions."
Donnie Fraser, of the Radical Inverness "Yes" campaign, said the car sticker ruling was ridiculous.
"I saw council guidance posted out last week about not having stickers on vehicles in council premises. That seemed ridiculous," he said.
"But how on earth can they stop people displaying stickers in public places? Are they going to stop workers putting them up in their homes as well?"
The council spokesman added: "For most staff, whatever they do in their own time is their own business.
"However, when somebody employed by the council is at work, they are restricted in terms of wearing badges, posting stickers on council vans or their own cars within a staff car park. It is so important to maintain that neutrality because we are all public sector workers.
"We are all paid by the public purse so in political referendums it is important that the public sector remains neutral."