The fans' group has added its name to the action which was lodged with the European Commission and the Belgian courts in May 2013.
City were the club hit hardest by UEFA for breaching FFP rules - they and Paris St Germain were each fined Â£49million and handed both restrictions on transfer spending and a reduction in Champions League squad size.
The action claims the FFP rules contravene European Union (EU) laws including the right to free competition.
A statement from MCFC Supporters Club, which has almost 15,000 active members and 168 branches worldwide, said: "Our members are consumers of the football product and it is as such that they denounce the EU competition law infringements caused by the UEFA break-even requirement.
"Far from implementing a true 'financial fair play', this rule is in fact a prohibition to invest that prevents ambitious owners to develop their clubs, that therefore shields the established European elite from being challenged (this elite being unsurprisingly the main sponsors of the UEFA rule) and that, consequently, puts additional financial pressure on supporters (higher prices and lower quality).
"With this UEFA rule, it is now almost impossible for any ambitious investor to take over a 'sleeping giant' and to turn them into the next Manchester City or Paris St Germain.
"In other words, the UEFA rule may be bad news for MCFC supporters, but it is even worse news for supporters of all clubs that do not today belong to the established European elite."
The legal action was brought by agent Daniel Striani and is being led by lawyer Jean-Louis Dupont, part of the legal team that won the Bosman ruling in the 1990s.
Source : PA