Senior SNP councillor Alasdair MacPherson was judged to have contravened the code over objectivity when questioning members of the public who were opposed to a new Wetherspoon pub in a former tax building in Stirling.
One campaigner who was objecting to the bar licence said Mr MacPherson was aggressive at a licensing board meeting. The politician was one of two referred to the Ethical Standards Commissioner by the council after complaints were received.
Mr MacPherson denied the claims at the time and said he backed the application because the company was "investing £1.5 million, providing 60 to 80 jobs and bringing back into use an eyesore of a building".
A second Stirling SNP councillor, Steven Paterson, was cleared of any wrong-doing in December.
The controversial application for the pub sparked complaints from residents and the licensed trade including rival brewing giant Greene King - which has a pub in the nearby Corn Exchange. The Watford-based chain eventually won the licence for the Spittal Street pub. Its Crossed Peels is due to open in July.
One campaigner, David Black, said at the time of the initial complaint: "I was the first objector to speak and was questioned. During this exchange, I was shocked, saddened, and angered by the way I was treated. My overall impression was that I was being bullied."
The Commissioner for Ethical Standards Stuart Allan reported to the Standards Commission for Scotland that he had concluded Mr MacPherson had "contravened the Councillors' Code of Conduct". The commission will now question him before deciding which if any sanction to take.
Mr MacPherson and Stirling Council declined to comment.