Among them is ancient history professor Josef Wiesehöfer, who derided it yesterday as "a propaganda inscription".

"It has become a very celebrated document," he said, "but Cyrus himself ordered it done, trying to make himself appear righteous. The real king was not more or less brutal than other ancient kings of the near east, like Xerxes, but he was cleverer."

In the UK, author and historian Tom Holland, who wrote about the rise of Cyrus in his book Persian Fire, joined the condemnation of the cylinder as a model text enshrining human rights.

"It's nonsense, absolute nonsense," he said. "The ancient Persians were not some early form of Swedish Social Democrats."

He added that conquering a huge empire in the ancient world did not come without a list of atrocities, and "he staged several salutatory atrocities when he invaded."

He added that the UN's adoption of the cylinder stemmed in part from a desire to claim some eastern roots "when it is so Western in its philosophical underpinnings".

But the UN, which has promoted the relic as an "ancient declaration of human rights" since 1971, when then Secretary General Sithu U Thant was given a replica by the sister of the Shah of Iran, stood by its importance yesterday.

"It is considered the first human declaration of human rights, guaranteeing the rights and welfare of the Babylonians after the Persians captured the city," Isabelle Broyer, the chief guide at UN headquarters, said yesterday.

Since then the scroll, which has been translated into all official UN languages, has helped burnish Cyrus's enduring reputation as a just and fair ruler, who favoured freedom of worship over bloodthirsty tyranny.

For all the criticisms of the Cyrus cylinder, it is unlikely to change perceptions of it in Iran, where Cyrus and the cylinder are regarded with intense national pride.

"It is a source of great pride," said Mr Holland, "but like many things said about Persia in Iran, it has to be taken with a big pinch of salt."