A British doctor has allegedly admitted prescribing performance-­enhancing drugs to 150 elite sportspeople, including Premier League footballers.

The Sunday Times claimed anti-ageing specialist Mark Bonar had been secretly filmed also confessing to supplying banned substances such as erythropoietin (EPO), steroids and human growth hormone to British Tour de France cyclists and a British boxing champion.

Bonar was said to have boasted about treating players from Arsenal, Chelsea, Leicester City and Birmingham City, although there is no evidence the clubs were aware of any alleged relationship he might have had with their footballers. He was alleged to have told an ­aspiring Olympic runner, who was working uncover for the newspaper: “Some of these treatments I use are banned on a professional circuit. So, you have to be mindful of that.”

The doping claims, if true, would represent one of the biggest ever drugs scandal in British sport. They were serious enough last night to spark an internal review at UK Anti-Doping after it emerged it had been tipped off two years ago that Dr Bonar was prescribing banned substances to sports stars but shelved a probe into the case due to insufficient evidence.

The five biggest sporting controversies everPlay! 02:08
UKAD was last night seeking The Sunday Times footage to ascertain whether it could now investigate further, although any alleged malpractice by Dr Bonar – who treats private patients in Knightsbridge – would be a matter for the General Medical Council.

The GMC has clear rules stating doctors should not prescribe sportspeople with performance-enhancing drugs.

Britain’s anti-doping agency first became aware of the 38-year-old in 2014 after imposing a ban on a sportsman who sought to reduce his suspension by offering to turn whistle-blower.

The athlete raised allegations against Dr Bonar but was unable to provide enough evidence for UKAD to take further action under its existing powers, which are limited to the world of sport. It also decided not to share the unsubstantiated information it had been given with the GMC, although it is understood the whistle-blower was encouraged to do so. The failure of any authority to follow up the case may prove controversial following The Sunday Times sting.

Culture secretary John Whittingdale said he was “shocked and deeply concerned” by the claims. “I have asked for 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,” he said. “There is no room for complacency in the fight against doping and the Government is looking at whether existing legislation in this area goes far enough.” Niall Dickson, chief executive of the GMC, said: “These are serious allegations and we will follow them up as a matter of urgency.”

Bonar denied doping sports stars to enhance their performance and said he had not breached GMC rules. He said: “The fact that some of my patients happen to be professional athletes is irrelevant. If they have proven deficiencies on blood work and are symptomatic, I will treat them. They are well fully aware of the risks of using these medicines in professional sport and it is their ­responsibility to comply with anti-­doping regulations.”