Mikhail Piotrovsky, the director of the Hermitage since 1992, accused museum staff who have access to the storage facility where the stolen items were kept.

He said that he felt stabbed in the back after items including historic gold and silver jewellery were found to be missing during an internal audit.

“Regrettably, it is already clear to me that the criminals apparently used museum staff to steal the precious objects,” he said. “We cannot yet determine the extent of the employees’ involvement. The presumption of innocence and the atmosphere of absolute trust in curators that has reigned in the museum in the past will have to change.”

None of the items was insured because they were in storage. The museum estimates the value of the 221 objects at $5 million, but art experts who have seen the full list told the newspaper Izvestia that the market value was 20 times that.

One of the four curators who had access to the looted part of the collection died in October, soon after the audit was announced. Irina Antonova, the director of the Pushkin Museum of Fine Arts, told the Moscow Times that the curator had died of a heart attack, but cautioned against accusing Hermitage employees until all the evidence had been examined.

Dick Ellis, a former Scotland Yard detective who works for the art-theft agency Swift-Find, said the objects that could not be sold openly would still have value on the black market.

He added that the museum had a reputation for not having a sophisticated cataloguing system.