A French intelligence operation to safeguard Niger's uranium industry and prevent weapons proliferation, inadvertently led to the forging of documents relating to an apparent clandestine uranium trade with Iraq, western intelligence officials say.

The operation, begun in 1999, reflected concern among several intelligence services that rogue states may have been trying to procure uranium. France was also concerned about the security of its own uranium supplies from Niger, as well as the security of the two French companies that control Niger's uranium industry.

Rocco Martino, an Italian businessman who has admitted that he has made a career out of "selling information", has held regular meetings with French intelligence officials in Brussels since at least 1999.

According to senior European officials, in 1999 he provided French officials with genuine documents which revealed Iraq may have been planning to expand "trade" with Niger. This trade was assumed to be in uranium, which is Niger's main export. It was then that Mr Martino first became aware of the value of documents relating to Niger's uranium exports. He was then asked by French officials to provide more information, which led to a flourishing "market" in documents.

He subsequently provided France with more documents, which turned out to have been forged when they were handed to the International Atomic Energy Agency by US diplomats.

The exposure of the forgeries appeared to undermine British government claims that Iraq had sought to buy uranium from Niger. US officials have distanced themselves from the claim, though the UK has insisted the forged documents were not part of their evidence.

According to senior intelligence officials, the forged documents were produced with the involvement of people familiar with Niger, and were created in 2000.

French officials have not said whether they know Mr Martino, and are unlikely to either confirm or deny that he is a source. According to the Sunday Times, which interviewed him under his pseudonym of Giacomo, Mr Martino said the Italian foreign intelligence service, the SISMI, had forged the documents and had arranged for them to be passed to him by an official of Niger's embassy in Rome. Mr Martino, who has not returned telephone calls since first contacted by the Financial Times a month ago, has retained personal contacts with some serving and retired officers in the SISMI since he briefly served in the intelligence services in the 1970s.

The Italian government yesterday strongly denied it had played any role in the forging of the documents or their dissemination, saying the accusations are "completely false".

Its statement also implied Mr Martino's claim to the Sunday Times that the documents were forged to justify the decision to invade Iraq is highly dubious as the market in documents - real or forged - was established several years before the war was discussed.

Intelligence experts also say that if the documents had been forged by a national intelligence service the quality would have been better and there would not have been discrepancies in them that led to them being exposed by the IAEA as fake.

One western intelligence official said: "This issue shows how vulnerable intelligence services and the media are to tricksters like Martino. He responded to a legitimate . . demand from the French, who needed the information on Niger. And now he is responding to a new demand in the market, which is being dictated by the political importance this issue has in the US. He is shaping his story to that demand."