Charlton, Fulham, Sheffield United and Wigan have confirmed they are taking legal advice following the Premier League's decision to fine West Ham over the signings of Carlos Tevez and Javier Mascherano.
The four - West Ham's rivals in the quest to avoid relegation from the Barclays Premiership - met in central London earlier toay to discuss the punishment, which many had expected to include a points deduction.
And a statement released by the four clubs and sent to the Premier League's board of directors confirmed: "You should understand we are separately in the process of obtaining legal advice arising out of the terms of the decision.
"You can expect to hear from us in relation to this in the early part of next week. In the meantime, all our rights in that respect are reserved."
Today's statement from the clubs said: "The board are given power under the rules to 'inquire into any suspected or alleged breach of these rules...The FAPL have a duty to act in good faith and with reasonable diligence.
"That duty extends to investigating an alleged breach of the rules where there is some apparently credible evidence of a breach.
"Furthermore, given the potential significance to our clubs of any further serious breach of FAPL rules by West Ham at this point in time, not to investigate immediately would be a breach by the League of their obligation of utmost good faith to us under FAPL rule B13.
"In the light of the above it is incumbent upon the board forthwith to investigate this matter."
The statement continued: "We require your urgent confirmation that that FAPL will act as set out above in this letter.
"If we do not receive that confirmation, we will take all such steps as are available to us to enforce and protect our rights, including taking urgent advice with a view to convening a meeting of the FAPL and/or bringing proceedings in court under Section 459 of the Companies Act 1985, on the basis that the affairs of the Company are being conducted in a manner which is unfairly prejudicial to us."