The legitimacy of Britain's first ever Tour de France win in 2012 by Sir Bradley Wiggins has been thrown into question as never before, as has the reputation and the future of the man who masterminded it and still leads Team Sky, Sir David Brailsford.

A devastating report into doping in sport by an influential group of MPs has made the stunning conclusion that it believes Team Sky was using drugs to enhance the performance of its riders, not just to treat medical need.

The comments come at the end of a two-and-a-half year-long investigation across British sport, but it is Wiggins, Brailsford and Team Sky that come in for the most damaging scrutiny.

During its inquiry the committee, which questioned Brailsford and other key figures within the road cycling team, was contacted by an anonymous source it describes as "well placed and respected".

The source, it's claimed, provided MPs with confidential material regarding the medicines policy at Team Sky, particularly for the 2012 season when Wiggins won the Tour.

This source alleges that Wiggins and a smaller group of riders trained separately from the rest of the team. The informant goes on to say "they were all using corticosteroids out of competition to lean down in preparation for the major races that season".

According to the report the same source also states that Wiggins was using these drugs beyond the requirement for any Therapeutic Use Exemption (TUE) - a medical certificate which allows an athlete to take a banned drug for health reasons.

Wiggin's former coach at Team Sky, Shane Sutton, gave evidence to MPs, but also wrote to them regarding Wiggins' use of the drug in question, triamcinolone, admitting that "what Brad was doing was unethical but not against the rules".

In April last year another anonymous whistle-blower made allegations about the inner workings at Team Sky. The identity of the source is known to the committee and is "well respected in the cycling community" it claims.

The whistle-blower, formerly a Team Sky employee, alleged that TUEs were used "tactically" by Team Sky "with an ultimate aim of supporting performance".

This and other evidence has led the committee to come to the stunning conclusion that "in 2012, we believe that this powerful corticosteroid was being used to prepare Bradley Wiggins, and possibly other riders supporting him, for the Tour de France".

"The purpose of this was not to treat medical need, but to improve his power to weight ratio ahead of the race."

In a statement responding to the allegations Wiggins said: "I find it so sad that accusations can be made, where people can be accused of things they have never done, which are then regarded as facts.

"I strongly refute the claim that any drug was used without medical need. I hope to have my say in the next few days and put to my side across."

The report had more than Wiggins in its sights - it also made observations that now put Brailsford's reign at the head of Team Sky under serious strain.

Talking about the allegations surrounding 2012, the Committee noted they "do not constitute a violation of the World Anti Doping Agency code, but do cross the ethical line that David Brailsford says he himself drew for Team Sky.

"In this case, and contrary to the testimony of David Brailsford in front of the Committee, we believe that drugs were being used by Team Sky, within the WADA rules, to enhance the performance of riders, and not just to treat medical need."

Equally damning for Brailsford, the report asks how he "can ensure that his team is performing to his requirements, if he does not know and cannot tell, what drugs the doctors are giving the riders?" And ominously goes on to say "David Brailsford must take responsibility for these failures."

Barely disguising their anger, Team Sky has responded to the Committee's most serious allegations in a statement.

Part of it reads: "The report makes the serious claim that medication has been used by the Team to enhance performance. We strongly refute this. The report also includes an allegation of widespread Triamcinolone use by Team Sky riders ahead of the 2012 Tour de France. Again, we strongly refute this allegation.

"We are surprised and disappointed that the Committee has chosen to present an anonymous and potentially malicious claim in this way, without presenting any evidence or giving us an opportunity to respond. This is unfair both to the Team and to the riders in question."

Wiggins has refuted all allegations. Credit: PA

The biggest problem both sides have in defending their own positions is the scandalous and shambolic medical record keeping at Britain's most decorated sports team.

All roads here lead to Dr Richard Freeman, the former British Cycling doctor who was allowed to resign from the organisation recently following a period of stress related ill health.

He was the doctor who ordered whatever was in the infamous Bradley Wiggins jiffy bag; he was the doctor who was incapable of uploading any medical data to a central file as was the team's protocol; and he was also the doctor whose laptop was stolen on holiday containing the only records in existence for each and every Team Sky rider he treated, including Bradley Wiggins.

Throughout the various inquiries, Dr. Freeman has been unable to contribute because of his sickness. He is however subject to an ongoing General Medical Council investigation and has very recently finally written a response to MPs when they told him they have new evidence regarding the contents of the jiffy bag.

Dr. Freeman said he could not respond because he didn’t know “the nature of the 'new evidence".' but he added: "Given the potential seriousness of the matters you have now raised, I am advised that mindful of the background of various investigations which are ongoing, I should not be expected to provide any further comment to you presently."

Wiggins said at the conclusion of the recent UK Anti-Doping investigation into the jiffy bag saga that he had been put through a "living hell" as a result of a "malicious witch-hunt".He was considering legal action then, so it is very likely his lawyers phone will be ringing furiously again today.

As for David Brailsford, he has ridden out many storms in the past 18 months and come through each and every one of them, albeit with a slightly diminished reputation. This time though it feels a knock down too far. There are only so many times you can get up off the canvas, whoever you are and whatever you've achieved.

Team Sky has found itself under increasing scrutiny. Credit: PA