Premier League clubs and officials were scrambling on Thursday to secure support before a totemic vote on the competition’s rulebook.

At a shareholders’ meeting in central London on Friday, clubs will be asked to pass modest changes to rules relating to associated party transactions (APTs), when clubs generate income from sources related to their ownership. If the rules are approved the competition is unlikely to be materially affected, but ramifications for the simmering conflict between the league and its serial champion Manchester City will be substantial.

City have declared their opposition to the rule changes – having previously taken the league to arbitration over its APT rules. They have lobbied clubs strongly for support, including two league-wide letters from their chief legal officer, Simon Cliff, which challenged the validity of the league’s plans. The league has spent weeks negotiating with clubs over their concerns, citing independent legal analysis from the KC Daniel Jowell to support its case.

Should City convince enough clubs to come with them, the ability of the league to act as an effective regulator will come into question, just as the hearing into City’s alleged 130 breaches of the rules is coming to a head.

Friday’s vote will require a two-thirds majority for it to go through which, in lieu of abstentions, means 14 clubs voting in favour. With City against the changes and Aston Villa having this week called for a delay to any amendments, another five clubs would be needed to vote down the measures. On Thursday night the outcome remained in the balance, but sources suggested the Premier League were growing in confidence that they had secured the necessary numbers.

A previous vote on APT measures, dealing with loans of players between clubs with shared ownership, was rejected a year ago. City were joined by Newcastle, Chelsea, Sheffield United, Burnley, Nottingham Forest, Everton and Wolves in voting against. The Blades and Burnley were subsequently relegated, and the Guardian understands Wolves are likely to vote in favour of the new rules this time.

The proposed changes follow criticisms brought by an arbitration tribunal last month. The tribunal found that rules which allowed owners to extend interest-free loans to clubs should have been treated as APT deals, and clubs were found to have been denied timely access to a database of prior deals when trying to strike APT arrangements. Criticisms over the timeliness of the league’s adjudications on such deals were also made.

City have argued that the tribunal’s criticisms have undermined the league’s entire APT apparatus. The league says the tribunal was an endorsement of its broader rules and that, given the proposed changes, they remain robust. Many clubs have grown weary of the internecine conflict and its associated legal costs.