Since signing for Hamburg in July 2005 from Ajax, van der Vaart, 24, has been courted by several top European sides including Spanish giants Real Madrid.

"We will not release van der Vaart, everyone at the club is very firm on that," Horst Becker, Hamburg's president of the board of trustees told daily newspaper Hamburger Morgenpost on Monday.

According to the paper, Valencia are eager to sign the attacking midfielder for a reported 14 million euros (19 million dollars).

Van der Vaart is under contract with Hamburg until 2010, but has refused to start negotiations with club bosses about an extension.

With a Spanish mother, van der Vaart, who has scored six goals in 40 appearances for the Netherlands wants to play in the Champions League and has said he "could not refuse an offer from Real.

Despite frequent injuries, van der Vaart has scored 17 goals in 46 Bundesliga appearances for Hamburg who finished third in 2005-06 and were seventh last season.