Strict guidelines have been issued to councillors on how to deal with the planning application for Southend United's new ground at Fossetts Farm.
Any Southend Council members who are season-ticket holders at the football club will be considered to have a conflict of interest and have been advised not to take part in debates on the application.
Those who attend occasional matches could also be affected, depending on how often they have been in the previous year.
However, the ruling is likely to have less of an effect than it would have done before recent changes to the council's constitution.
Large or controversial planning applications are now decided by the 15 members of the development control committee, instead of the full council, and no member of the committee is a season ticket-holder.
Lib Dem group leader Graham Longley, a Blues fan, said: "Since the rest of us will have no say in the matter, we will be able to make whatever comments we like."
John Williams, monitoring officer for the council, said he had discussed the issue with the Standards Board for England.
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