Investigators have made unannounced visits to two clinics run by Britain's most successful test-tube baby doctor.
The police-accompanied inspections were carried out by the Human Fertilisation and Embryology Authority (HFEA) with a court warrant.
The HFEA says this is part of regulatory action and that it has been contacted by a whistleblower.
One of the clinics was secretly filmed by Panorama offering unproven treatment to women, potentially risking health.
IVF Undercover, which was broadcast on BBC One on Monday night, has undercover footage from the Assisted Reproductive and Gynaecology Centre (ARGC), run by Mohamed Taranissi who has produced 2,300 babies in seven years.
But he also ran an unlicensed clinic from December 2005 for almost a year.
The chief executive of the HFEA Angela McNab told a news conference: "For some time the HFEA has been taking regulatory action against the clinics run by Mr Taranissi. Whilst we have tried to work with his clinics to get the information we require to do our job we have been challenged by his clinic and his lawyers at almost every step of the way.
"Information has continued to come to light during this process and this morning I was able to go to court to secure a warrant. This will allow us to gain unimpeded access to the clinics run by Mr Taranissi.
"As we speak two inspection teams from the HFEA have gone simultaneously into these two clinics with police officers in attendance to carry out an unannounced inspection of the two buildings and to secure the information that we need and are entitled to under the law.
"We've received information from whistle blowers who appear to have been working in the centre.
"And we're also aware of the separate allegations made in the BBC Panorama programme which will need investigation."
Mr Taranissi gave a statement in response to the HFEA inspections.
He said: "We can confirm that inspectors from the HFEA and the Healthcare Commission visited ARGC and RGI today.
"Mohamed Taranissi cooperated fully with the inspection team and will continue to do so.
"Mr Taranissi is happy to make all records available to the HFEA as he has never had anything to hide.
"Mr Taranissi is confident that HFEA checks on his records will lead to them reconfirming what they have always said in the past - that his methods work, as shown by his clinics topping their league tables for patient results every year since 1995.
"Mr Taranissi welcomes the HFEA's decision to allow him to continue his important work, and wants to reassure all his patients that he will not let any of this affect the level of treatment and care they are receiving."
And he has rejected the criticisms levelled at him in Panorama.
Fertility experts viewed Panorama's footage from the ARGC.
'Makes you weep'
Watching some of the footage, Lord Robert Winston said: "It makes you weep for the medical profession. It's a failure of regulation."
But Mr Taranissi, whose wealth is calculated to be £38m, told Panorama after the undercover filming: "There's a lot of regulations that seem to apply to us more than other people.
"We're not against regulation, we just hope that we can finish with this and move forwards for everybody because it takes a lot of time from my time which I need to devote to patients because that's what I am good at and that's what I want to continue to do - provide results for people."
The experts watched Panorama's secret filming and said they were disturbed when they saw:
A 26-year-old undercover reporter offered IVF treatment at the ARGC, which could cost her up to £10,000 in some circumstances, even though neither she nor her partner had any history of fertility problems. A second undercover patient with a similar medical status is correctly told that at her age she does not require treatment
The 26-year-old was then offered a treatment involving a blood transfusion of a concentrated mix of human antibodies. One expert said it was impossible to know what the antibodies could do to a baby
Blood tests costing £780 involving 18 phials of blood from the arm of the 26-year-old which the experts describe as incapable of revealing fertility problems
A senior clinician telling the reporter her blood test revealed levels which indicated treatment but one expert analysed the results as "all completely normal"
Panorama also found out that Mr Taranissi was risking a jail term by continuing to carry out IVF treatments at a second clinic called the Reproductive Genetics Institute (RGI) which no longer has a licence.
It was not renewed at the end of 2005 due to a lack of required data. It is a criminal offence to operate in an unlicensed clinic.
Using the Freedom of Information Act, Panorama obtained figures showing how Mr Taranissi treats some older women at the RGI.
The birth rates there are consistently much lower than the ARGC. Mr Taranissi says this is because they require specific treatments and not because this helps boost his success rate at his main clinic.
Mr Taranissi said: "The Panorama programme is wrong on many key facts.
"The programme makers question the efficacy of immune testing in IVF, yet I am open about the fact that it is indeed one reason for my success rates.
"Panorama says that my second clinic, RGI, operated for a while without a licence. As explained to them, this is a matter of legal dispute.
"The clinic in question was offered a three-year licence. On the form accepting this, I said I wish to make representations.
"The HFEA regulator seemed to interpret this two months later as me declining the licence, and the matter has been with the lawyers ever since."
The chair of the British Fertility Society, Mark Hamilton, said: "We can't comment on any individual case but any exploitation of distressed and vulnerable patients is absolutely unacceptable.
"The fertility sector is probably the most regulated sector in UK medicine and the HFEA has said today that the vast majority of clinics in the UK comply well with these standards.
"As a society we expect our members to uphold high standards. We support innovation where treatment is in the framework of a properly conducted, ethically approved clinical trial."
IVF Undercover was broadcast on Monday 15 January at 2030 GMT on the Panorama website and BBC One.
If you are affected by any of the issues in the programme and would like to talk to someone in confidence for further information and support, please call the BBC Action Line on 0800 077 077. Lines opened at 2100 GMT on Monday 15 January for a week and may be busy but the Action Line will be open from 0730 GMT until 0000 GMT. All calls are free and confidential.
The HFEA has also set up a helpline on 0207 291 8222. Or you can email email@example.com for advice.
Infertility Network UK also opened a helpline tonight on 08701 188 088.