Mobile phone group Vodafone is ending a four-year shirt sponsorship deal with Premiership club Manchester United.

The deal, worth around £9m a year, will now end in May 2006, two years earlier than planned.

"Manchester United have agreed to end their shirt sponsorship. The Club believes that the shirt sponsorship market has greatly increased in recent years, while Vodafone wishes to build on its successful sponsorship of Manchester United in new, exciting areas," both parties said in a joint statement.

United commercial director Andy Anson said: "The Manchester United shirt is the most iconic in sport. The club feels that in the current market there is a genuine chance to attract significant additional investment.

"Initial soundings and discussions with a number of world class potential partners have been very encouraging and we are confident of securing a new deal in the coming months."

Vodafone has signed a three-year agreement to sponsor the UEFA Champions League.

The deal, starting next July, will see Vodafone become both an official partner and the official mobile network of the tournament.

United's shirt sponsorship was the fifth-biggest in Europe.

The largest current shirt sponsorship deal in European football is the £110m, five-year contract Italian giants Juventus have with Libyan oil firm Tamoil.

Real Madrid are paid £14m a year by German engineering giant Siemens.

German champions Bayern Munich earn £11.4m a year from its deal with mobile phone group T-Mobile, while Premiership champions Chelsea collects £9m a year from South Korean electronics company Samsung.