A panel has ruled that the chief whip of the Labour Party in Waltham Forest did try to fix a planning application vote by pressuring a colleague with a text message - but has cleared him of all other allegations of wrongdoing.
Cllr Azfal Akram was accused of several attempts to sway the outcome of decisions made by the council's planning committee, which is supposed to make decisions independently of party loyalties.
But a 'determination' disciplinary panel of three councillors has now ruled that only one of the allegations was true.
They judged that Cllr Akram did try to influence his colleague Cllr Karen Bellamy on the planning committee over an application to convert Leytonstone's Colgrave Arms pub into a mosque, which was subsequently approved.
He sent a phone message to Cllr Bellamy in the middle of a meeting in September 2012, which was held to vote on the plans, saying "I hope you are going to support this one".
Cllr Akram said the text was a tongue-in-cheek jokey reference to an earlier discussion the pair had on mosque applications, but the determination panel was not convinced.
However Cllr Akram was cleared of allegations that he also tried to fix two other applications involving mosques.
Cllr Peter Barnett, the Labour chair of the planning committee who made the allegations, said Cllr Akram verbally threatened Cllr Bellamy with deselection if she did not support one of those proposals.
He also claimed Cllr Akram used eye contact and gestures to pressure Cllr Bellamy and Cllr Ebony Vincent during the meeting, although council officers called as witnesses did not see this.
Cllr Akram denied all the claims. He said there was either a "wider conspiracy" at the council to get rid of him or that Cllr Barnett had a grudge because he lost his position as chief whip in 2008.
Cllr Akram was suspended as Labour chief whip last autumn and the Labour group is now due to meet within the next few weeks to decide what to do next.
Details of the determination panel's ruling and Cllr Akram's punishment are set to be published within the next seven days.
Cllr Barnett said the allegations had the potential to expose the council to legal challenge over other controversial planning applications, such as the Walthamstow Stadium housing development.
The Guardian has approached Cllr Akram for a comment.