Irish racehorse magnate John Magnier, who is involved in a bitter legal dispute with Manchester United boss Sir Alex Ferguson, has increased his stake in the Premier League club.

Magnier and fellow Irish tycoon J.P. McManus, increased their stake in the English champions to 25.49 percent on Monday, increasing speculation that they are planning a takeover bid for the club.

Cubic Expression Ltd, an investment vehicle controlled by the Irish millionaires, said in a statement to the stock exchange it had bought 3,256,944 million United shares, to take its total holding to 66,543,837 shares.

Magnier is currently involved in a legal battle with United manager Alex Ferguson row over the stud rights to racehorse Rock of Gibraltar.

United have been the subject of constant takeover speculation in recent months.

U.S. sports entrepreneur Malcolm Glazer, who allso owns Tampa Bay Buccaneers, is the second-biggest shareholder with 14.31 percent.