Inside track on Man Utd row Man Utd to review transfers The men behind the saga

The Irish horseracing tycoons duo have built up a 25.49% stake in the club and Henk Potts, of Barclays Stockbrokers, thinks they will make a full bid soon.

Potts claims that could mean a major reshuffle at United, with Sir Alex Ferguson's role as manager possibly thrown in doubt.

"I can see them taking control and running the club in a different way," said Potts.

He added: "When that happens they will remember who their friends were and who exactly didn't help them out.

"The board members and Sir Alex Ferguson may find their job prospects limited.

"I certainly believe that Magnier and McManus will make a full bid for Manchester United.

We are going away from Plcs and going back to rich businessmen taking over football once again Henk Potts Barclays Stockbrokers

"They are in a fantastic position as they own a quarter of the company.

"You wouldn't want to own 25% of Manchester United as an investment - you would want to own all of Manchester United or you would try and make a profit.

"We are going away from Plcs and going back to rich businessmen taking over football once again."

As the club's biggest shareholders, Magnier and McManus are said to have asked that all recent transfers at the club be reviewed.

On Monday, United promised an internal enquiry into their recent dealings and also stressed their policies were "the most rigorous in football".

But a source close to the duo said Magnier and McManus were still not satisfied with the club's pledge.

"It did nothing to alleviate the legitimate concerns of shareholders," the source told Reuters news agency.

The two men sent a letter to United's board asking 63 questions about how the club is run.

They are said to be questioning whether manager Ferguson should be offered a new four-year contract worth £4m and could demand an extraordinary general meeting to discuss the issue.

Man Utd defend transfer policy

United's Supporters' Association accused the club's biggest shareholders of running a "dirty tricks campaign" against Ferguson.

And fans in Northern Ireland have give Ferguson their full backing, saying they are disappointed by the actions of Magnier and McManus.

"We are embarrassed about the problems these Irishmen are causing Manchester United."

Magnier is in dispute with Ferguson over stud fees for the stallion Rock of Gibraltar.

Press reports say Ferguson is likely to sign a new contract this week, but that it will be the one-year rolling deal that the Irish shareholders have demanded, rather than the longer contract Ferguson wanted.