Tony Blair's former election agent has been suspended as a councillor for a month, for swearing and threatening a Labour colleague. John Burton, 67, was reported to the Standards Board for England following an outburst at Sedgefield Borough Council in October 2006.
A tribunal heard that he had warned Kester Noble in colourful tones that he would be deselected if he did not back a £20m housing scheme.
The hearing was told it was a "one-off event in an otherwise exemplary political career".
Mr. Burton, who was the former PM's constituency agent from 1983 until Blair stepped down as an MP this summer, was reported after his comments were overheard by another councillor.
The Adjudication Panel for England, meeting in Darlington on Tuesday, heard that Mr. Burton had sworn at fellow Labour councillor Mr. Noble, and told him he was putting pressure on him.
A tribunal heard that Mr Burton said to Mr Noble, the then (Labour) deputy leader of Sedgefield County Council: "I'm putting ****ing pressure on you. [The application] is good for the village. It's what the people want and there's an election coming."
The tribunal heard the planning application, for 112 homes on land outside Trimdon, was rejected by 23 votes to four - Mr. Noble was among those who opposed it.
Mr. Burton left the meeting before the vote - after declaring an interest as a member of Trimdon Parish Council and the Trimdon 2000 community project.
In March, Mr. Noble was deselected as a Labour candidate for the Old Trimdon and Fishburn ward.
The adjudication panel rejected accusations that Mr. Burton had broken the code of conduct by speaking in favour of an application in which he had an interest, and also rejected any suggestion he had been responsible for Mr. Noble's deselection.
But it found that the threats and offensive language used by Mr. Burton had brought his office into disrepute and did breach the code of conduct.
The month-long suspension begins immediately. Mr. Burton said he did not want to comment on the ruling.