The sculptures were once part of the Parthenon

Two Belgian senators, Francois Roelands du Vivier and Paul Wille, say an international campaign is the only way to get the sculptures returned to their city of origin.

Their campaign backs up a call by UK politicians and actors, including Tony Banks, Michael Foot and Vanessa Redgrave, to hand the sculptures back.

The marble friezes are currently in the British Museum in London, which says it is the rightful owner and that Lord Elgin "saved" them from destruction when he removed them in 1799.

The Belgian senators said the museum was being "stubborn", and were due to reveal a list of 135 supporters on Wednesday.

The public will be invited to add their signatures to a petition via a website, and the names will be handed to the British ambassador in Brussels in June.

Bill Clinton and Vladimir Putin have both supported the return

The marbles are the most important example in a wider desire to return artefacts to their places of origin, the senators said.

'Goodwill'

Liberal Democrat MP Richard Allan, who launched the Parthenon 2004 campaign in the UK, said: "The launch of Parthenon 2004 in Belgium shows that return of the Parthenon Marbles to Greece is of global concern.

"If we are going to fully embrace being a part of Europe, then we should make this gesture to Greece.

"It provides the perfect opportunity for the British government to demonstrate that it is a key player in international co-operation and goodwill."

Bill Clinton and Vladimir Putin are among the international politicians who have previously said they support the return, Mr Allan said.

A new museum to house the marbles is being built in Athens

He added another 600 signatures had been collected in the European Parliament.

But the British Museum's director, Robert Anderson, has turned down calls for the sculptures to be returned.

They "belonged to the British Museum and the international public who come to the British Museum", he said recently.

Despite the refusal, Greece is building a new �29m Acropolis museum in which it hopes to house the friezes.

Known in Greece as the Parthenon sculptures, they date from between 447 and 432 BC and depict the most formal religious ceremonies of ancient Athens.

'Rescued'

They were removed from the Acropolis two centuries ago by the then British ambassador Lord Elgin.

Mr Anderson recently wrote in The Times that Elgin had been unjustly "defamed" by the campaign to restore the pieces to Greece.

He added that at Elgin's time, the Parthenon was a ruin, having been damaged by an explosion at the end of the 17th Century.

"We are indebted to Elgin for having rescued the Parthenon sculptures and others from the Acropolis from the destruction they were suffering," he wrote.