The doctor at the centre of allegations he prescribed performance-enhancing drugs to sports stars has described the claims as "false and very misleading".
A Sunday Times report alleged Dr Mark Bonar claimed to have treated more than 150 sportsmen and women - including Premier League footballers, British Tour de France cyclists, tennis players and a British boxer - with banned substances including EPO, human growth hormone and steroids.
A Twitter account purporting to belong to Bonar on Sunday night, although not verified, read: "The @SundayTimesNews allegations are false and very misleading. I have never had a relationship with any premier football club or player.
"I have never prescribed Androgen therapy for the purpose of performance enhancement.. I treat symptomatic men with low Test levels."
Androgen therapy is a class of replacement therapy of hormones such as testosterone which could have performance-enhancing benefits.
An independent inquiry into the allegations is expected to formally begin within the next 24 hours.
British Culture, Media and Sport Secretary John Whittingdale demanded an urgent investigation into UK Anti-Doping's (UKAD) response after the newspaper claimed the organisation was given information about the doctor's alleged doping activities - which he denies - two years ago but failed to take action to stop him.
UKAD is in discussions with officials from Whittingdale's department over who should lead the inquiry and what its remit will be.
Although UKAD was made aware of general allegations made against Dr Bonar by an unnamed sportsman in April and May of 2014 the information was vague and not at the level of detail reportedly uncovered by The Sunday Times.
UKAD was subsequently supplied with handwritten prescriptions apparently issued by Dr Bonar which were given to an independent medical expert for analysis.
"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," UKAD chief executive Nicole Sapstead said.
"After assessing all the evidence, as per the National Intelligence Model, UKAD did not believe that there were grounds, at that point, to refer the case to the General Medical Council (GMC)."
UKAD recommended the sportsman who brought the allegations to its attention gather more information and pass it on to the GMC - the national body responsible for the registration and conduct of doctors - "if appropriate" as the doctor was outside its jurisdiction.
It is understood UKAD has now made a request to The Sunday Times for full disclosure of all its evidence.
The GMC has confirmed while Bonar is registered with it, he does not have a current licence to practise medicine in the UK and the Omniya Clinic in London, where the doctor rented private consulting rooms to treat his patients, said it ended his professional services agreement on Friday after learning he does not hold a current licence.
"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," GMC chief executive Niall Dickson said.
An FA spokesman on Sunday night said: "These are very serious allegations. As such, The FA welcomes UK Anti-Doping's decision to immediately launch an independent review into the matters raised by the Sunday Times.
"The FA is fully committed to maintaining the integrity of English football and will work with UKAD and other relevant agencies in seeking to do so.
"The FA urges anyone with information that may be relevant to come forward as soon as possible."