Manchester United may have to cough up the £12 million paid by Chelsea for John Obi Mikel two seasons ago, it has been revealed.

The Times says Chelsea could be refunded the £16 million transfer fee paid to United and Lyn Oslo for Obi Mikel if Morgan Andersen, a former Lyn director, is convicted of forging the Nigeria midfield player's first professional contract.

It is understood that Svein Holden, a Norwegian public prosecutor bringing the case against Andersen in a fraud trial in Oslo this week, will argue for the settlement to be cancelled on the grounds that Mikel's contract with Lyn was invalid, making him available as a free agent.

Chelsea are monitoring the trial, but cannot comment publicly because they signed a confidentially agreement when the compensation package was agreed in June 2006, with United and Lyn receiving £12 million and £4 million respectively to facilitate Mikel's move to Stamford Bridge.

Andersen's trial is expected to last two weeks and Mikel and his agent, John Shittu, could be called to testify via videophone. Andersen denies all the charges.