Relatives of artist JMW Turner have threatened to take back his paintings from the Tate and the National Gallery, claiming the museums have breached the conditions of his will.

Descendants accused the galleries of flouting Turner's wishes by placing his paintings and drawings in rooms containing the work of other artists.

Turner's will reportedly specified that his collection, now worth about £500m, should be contained in rooms within the National Gallery set aside specifically for that purspose.

Instead, all but nine of his works were moved to Tate Britain.

It is a deeply complex will

Tate Spokesman

The Tate's Clore Gallery, where most of the 20,000 drawings and 300 paintings are housed, recently began displaying other artists' work alongside the Turners, further angering the family.

But a spokesman for the Tate said it has yet to receive any legal letters laying out the family's grievances.

"We haven't had any letter to the effect that they're taking action, so we don't know exactly what the legal implications are," a spokesman said.

He described Turner's will as "deeply complex", saying the artist's instructions were not clear cut.

Turner wanted his work to hang in the National Gallery

Turner wrote the will in 1848, three years before his death. The document said that his offer to the gallery would be revoked after 10 years if the terms were not met.

The family has contacted a lawyer and is seeking an act of parliament to bring the collection under one roof, according to news reports.

But the Tate's spokesman said Turner's profile has never been higher thanks to its efforts.

"In terms of access to Turner's legacy, it is unparallelled," he said, noting that the entire bequest was recently launched online.