Two fertility clinics run by Mohamed Taranissi, Britain's most successful IVF doctor, were inspected unannounced yesterday, after one of the clinics was filmed offering unproven treatment to women.

Police accompanied Human Fertilisation and Embryology Authority inspectors during the visits to the London-based clinics ­ the Assisted Reproduction and Gynaecology Centre and Reproductive Genetics Institute ­ run by Mr Taranissi, who has produced 2,300 babies over the past seven years and is reportedly worth £30m.

The HFEA said it obtained search warrants as part of "regulatory action" after being contacted by "whistleblowers who appear to have been working in the centre".

The investigation comes after staff at one of the clinics were filmed for the BBC's Panorama allegedly offering a 26-year-old undercover journalist "unnecessary and unproven" IVF treatment, despite she and her husband having no history of fertility problems.

Mr Taranissi is also accused of continuing to operate the Reproductive Genetics Institute after its licence was not renewed at the end of 2005 due to a lack of required data, the programme claims. Mr Taranassi denies the allegations. He said: "My clinics have always been well run, safe and reputable."