About 4,000 of the objects taken from the museum had been recovered in Iraq. But illustrating the international demand for such antiquities, Dr Curtis said around 1,000 had been confiscated in the US, 500 pieces had been impounded in France, 250 in Switzerland and 200 or so in Jordan.

Other artefacts have been retrieved from surrounding countries such as Syria, Kuwait, Iran and Turkey. None of these objects has yet been sent back to Iraq.

Other items had been destroyed or stolen from enormously important archaeological sites such as those at Nimrud and Babylon. "Some of them resemble minefields there are so many holes," Dr Curtis said.

Random checks on Western soldiers leaving the area had found some in illegal possession of ancient artefacts.

But he said: "I don't think large numbers of antiquities from these sites have been passing through London. I'm not aware of large amounts being in the salerooms in London."

The full extent of the damage has been impossible to gauge so far because of the deteriorating security situation.

The director of the Iraq National Museum has been forced to seal his storerooms because it is currently too dangerous for his staff to start work on an inventory of the material that has been returned.

An international mission planned under the auspices of Unesco, the United Nations' cultural organisation, with advice from experts at the British Museum, has been unable to start work for similar reasons.

The delays all make it more likely that material will continue to be lost from the country's archaeological sites, some of which have been permanently damaged by war.

Two years ago, the BBC documentary-maker and historian Dan Cruickshank suggested that museum staff had been involved in, or permitted, the looting . But Dr Curtis said he thought staff had nothing to do with the thefts. There was confusion, he said, because museum staff had emptied cases of transportable goods and hidden them in secret storerooms before war broke out.

A spokesman for the London market said everyone in Britain was acutely aware of the dangers of buying goods from Iraq and there were very strong deterrents. The Cultural Objects (Offences) Act of 2003 meant anyone trading in illicit objects facedup to seven years in jail