A minister has ordered an urgent investigation following claims a British doctor was secretly filmed telling how he prescribed performance-enhancing drugs to sports stars.
The London-based doctor, named by The Sunday Times as Mark Bonar, claimed he treated more than 150 sportspeople with banned substances including EPO, human growth hormone and steroids, according to an investigation by the newspaper.
He allegedly said he treated footballers at Premier League clubs including Chelsea, Arsenal and Leicester City along with British Tour de France cyclists, tennis players and a British boxer.
However, there is no independent evidence the sports stars received any banned treatments and the football clubs have denied the claims.
Dr Bonar, 38, labelled the allegations "false and very misleading" and insisted he had not breached rules laid out by the General Medical Council (GMC), the body which regulates doctors.
The GMC has confirmed that while Dr Bonar is registered with them, he does not have a current licence to practise medicine in the UK.
The doctor is also facing disciplinary hearings that could see him struck off for a separate allegation of providing a patient with inadequate care, the GMC said.
The Sunday Times reported that the UK Anti-Doping (UKAD) watchdog was given information about the doctor's alleged doping activity two years ago but failed to take action to stop him.
John Whittingdale, the Culture, Media and Sport Secretary, said there was "no room for complacency" in tackling doping, adding that the Government was already reviewing existing legislation.
He said: "I have asked for there to be an urgent independent investigation into what action was taken when these allegations were first received and what more needs to be done to ensure that British sport remains clean."
UKAD officials confirmed they received information from a sportsman, who has not been identified, that named Dr Bonar, in April and May 2014 and began an investigation.
The body said it could not pursue the investigation as the doctor fell outside their jurisdiction and they did not believe there were grounds to refer the case to the GMC at the time.
UKAD said it had recommended the sportsman gather more information and pass it on to the GMC "if appropriate".
Then in October 2014 the sportsman produced handwritten prescriptions he said were issued by Dr Bonar. After expert analysis UKAD stood by its decision not to refer the case to the GMC.
Nicole Sapstead, UKAD chief executive, said: "Following those interviews and an investigation, UKAD found that there was nothing to indicate that Dr Bonar was governed by a sport and UKAD had no other intelligence to corroborate the sportsman's allegations."
The watchdog's chairman, David Kenworthy, said an independent review of the allegations will examine the information passed to the organisation in 2014 to discern if the proper procedures were followed.
UKAD said the exchanges in 2014 were the first and only time Dr Bonar's name had been brought to its attention.
In a series of messages posted on what appears to be his Twitter account Dr Bonar denied The Sunday Times' allegations, adding: "I have never had a relationship with any premier football club or player."
He also denied prescribing hormone replacement therapy to sportsmen to enhance their performance, writing: "I have never prescribed Androgen therapy for the purpose of performance enhancement. I treat symptomatic men with low test levels."
Commenting on the doping allegations, Niall Dickson, chief executive of the GMC, said: "These are serious allegations and we will follow them up as a matter of urgency."
On a separate matter Dr Bonar is also facing disciplinary action in April following claims he failed to take proper responsibility for a patient's care.
The allegation dates back to December 2013 and relates to the care of a patient with incurable cancer. It is not linked to the doping claims.
Dr Bonar has insisted that he has not breached the GMC's code.
The Omniya Clinic in Knightsbridge, west London, where the doctor rented consulting rooms to treat his private patients, said it ended his professional services agreement on Friday after learning he does not hold a current licence.
The clinic said, apart from the undercover athlete The Sunday Times used, there was "absolutely no trace of a single high-profile sportsman or woman who has been treated or been seen at the clinic by Dr Bonar".
They added the clinic was never made aware UKAD had been handed information alleging impropriety and condemned doping "vigorously".
Arsenal, Chelsea and Leicester City said they were "disappointed" by the claims which they denied and stressed their teams followed strict anti-doping protocols.
The Sunday Times report also claimed former Chelsea fitness coach Rob Brinded had "collaborated" with Dr Bonar, but in a statement he denied the allegations "categorically" and distanced himself from the doctor.