AstraZeneca is handing over documents to the Serious Fraud Office (SFO) as part of an investigation into alleged bribes paid out to Saddam Hussein’s deposed Iraqi regime.

The SFO turned its attention to the pharmaceutical giant – which has its main UK research and development site at Alderley Park – while examining possible breaches of the oil-for-food sanctions in the Middle East.

The investigation was sparked by a damning United Nations report which listed more than 2,200 companies worldwide, including AstraZeneca, that may have been connected to bribery or "kickbacks" to Iraq.

AstraZeneca has remained tight lipped about the details of what documents have been asked for, and what level of involvement it has in the investigation, but the company has denied any wrongdoing and said it will cooperate fully with the SFO.

Two other British pharmaceutical firms; Eli Lilly and GlaxoSmithKline, have also been asked to provide documents.

The oil for food scheme was set up allow the Iraqi government to sell limited amounts of oil to buy foreign food and medicines.

But Paul Volcker, the former chairman of the US Federal Reserve, said in his 2005 report for the UN that it had become corrupt as Saddam Hussein’s regime demanded payments from foreign companies in return for lucrative contracts.

The investigation, which could take years to complete and is expected to cost around £22million, has been predicted to become one of the biggest undertaken by the SFO.

An AstraZeneca spokeswoman said: "AstraZeneca has received a request from the Serious Fraud Office for documents as part of its review of the oil for food programme in Iraq. The company will be providing the documentation.

"We deny any allegation of unethical behaviour on our part in our trading relationships with Iraq. AstraZeneca sent a consignment of medicines originally requested by the Hussein government under the United Nations Oil for Food Programme.

"Most of the consignment was delivered after the coalition forces of the US and UK had taken control of the country. The consignment was sent with all relevant United Nations permissions and UK Government Department of Trade and Industry export licences in place."