Sir Alex Ferguson is adamant that Manchester United’s bid to retain the Premiership title will not be affected by what he describes as “off-field nonsense”.

Ferguson is locked in a legal dispute with Irish horseracing tycoon and United shareholder John Magnier over the stud rights to Rock of Gibraltar. The feud has escalated in recent weeks with Magnier and his business partner JP McManus uppping their stake in United to 28.9%.

“I’m determined nothing will interfere with my focus on my work,” Ferguson said.

“Following all the off-field nonsense I am in good shape after the massive message of confidence from the fans.”

Ferguson’s pledge came on the same day that Magnier and his business partner J P McManus confirmed they had increased their stake in Manchester United. Through their investment company, Cubic Expression, the pair now own 28.89% of Manchester United plc.

The pair are not thought to be interested in assuming outright control at Old Trafford but they are looking for a say in the way the club is run and to that end, they want three representatives on the United plc board.

That would allow the Irish duo to exert greater influence, not only on Ferguson’s future at the helm, but in the running of the club as a whole.

United’s battle to retain the Premiership was not helped by last night’s 3-2 home defeat to Middlesbrough – a result which leaves Ferguson’s side trailing leaders Arsenal by 5 points.