An inquiry has been ordered into claims a doctor prescribed banned drugs to 150 sportsmen, including Premier League footballers.
Mark Bonar charged stars thousands of pounds for performance-enhancing drug programmes, according to an investigation by The Sunday Times.
Culture Secretary John Whittingdale has called for an urgent inquiry, saying he was "shocked and deeply concerned".
Part of the inquiry will focus on the taxpayer-funded UK Anti-Doping (UKAD) watchdog, which was apparently given evidence on the matter two years ago but failed to take action.
Dr Bonar was secretly filmed allegedly making a series of disclosures in meetings with undercover reporters from the Sunday newspaper.
John Whittingdale has ordered an inquiry
In the meetings, the doctor claimed his network of "clients" included a cricketer, cyclists and tennis players.
Several Premier League footballers were also among his clients, the doctor told reporters.
He claimed he had treated Arsenal, Chelsea, Leicester City and Birmingham City players - but the clubs have strongly denied the allegations.
And The Sunday Times makes it clear it has no independent evidence that Dr Bonar actually treated the players and only has his word for it.
Since 2010, he claims to have treated more than 150 sports people from the UK and abroad.
Banned substances that were allegedly prescribed included erythropoietin (EPO), steroids and human growth hormone.
London-based Dr Bonar denied the allegations when they were put to him by the newspaper.
He added he had not breached rules laid out by the General Medical Council (GMC).
Mr Whittingdale 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.
"There is no room for complacency in the fight against doping and the Government is already looking at whether existing legislation in this area goes far enough.
Chief executive of UK Anti-Doping Nicole Sapstead
"If it becomes clear that stronger criminal sanctions are needed then we will not hesitate to act."
UK Anti-Doping said it was "shocked" by the allegations in The Sunday Times and would order an independent review.
Chief executive Nicole Sapstead said UKAD began an investigation into Dr Bonar in 2014 after information supplied by a sportsperson.
The sportsperson went on to supply UKAD with handwritten prescriptions, allegedly issued by Dr Bonar.
But Ms Sapstead said the organisation was unable to act because Dr Bonar was not governed by any sport.
UKAD said the doctor fell outside its jurisdiction and it did not believe there were grounds to refer the case to the GMC.
GMC chief executive Niall Dickson, said: "Dr Bonar does not currently hold a licence and is therefore unable to practise medicine in the UK.
"Any doctor without a licence who continues to carry out the privileged duties of a doctor is committing a serious breach of our guidance, and potentially a criminal offence.