Portsmouth and West Ham are facing a possible points deduction after breaching Premiership rules by fielding ineligible players, according to reports.

The Daily Mail claims that a number of top-flight clubs are questioning whether the appearances of Javier Mascherano and Carlos Tevez for West Ham and Manuel Fernandes for Portsmouth were in violation of Premiership Rule U18.

Rule U18 states that: "No Club shall enter into a contract which enables any other party to that contract to acquire the ability materially to influence its policies or the performance of its teams."

This covers players owned by a third party, like Mascherano and Tevez, who are part owned by Kia Joorabchian, and Fernandes, who is partially owned by a private company called Global Sports Agency.

One possible breach of the rule is the widely-reported claim that if Manuel Fernandes played three consecutive games for Portsmouth, a sell-on clause in his contract would be automatically triggered.

Everton, who have taken Fernandes on loan for the remainder of the season, are one club reported to be demanding the points from their clash with Pompey earlier in the season, in which Fernandes featured.

Meanwhile, complications over the transfers of Mascherano and Fernandes in the January transfer window have aroused suspicion over the players' roles for West Ham - and a group of clubs are now preparing to launch a legal challenge if they feel they have been unfairly disadvantaged.

The Premier League has insisted that they are unaware of on any breach of the rules.

"With what has been presented to us we haven't allowed anything that would transgress our rules," said a league spokesman.

But the Daily Mail claim they have come into a possession of a letter warning West Ham they risked a points deduction if they failed to produce the necessary documents for the transfers of Tevez and Mascherano in the summer.

The letter, obtained by the Mail from the Premier League, says they have contacted the 20 top-flight chairmen this week and offered them a 14 day amnesty to produce any contracts which breach rule U18 and were not disclosed when the player was registered.