The world of tennis has been hit by claims of widespread match-fixing at the top level of the sport.
The names of 16 players have been flagged repeatedlyto the Tennis Integrity Unit (TIU) over the last decade amid fears they have thrown matches, according to an investigation by the BBC and internet media company BuzzFeed.
The investigation suggests that the suspects include Gland Slam singles and doubles champions and the alleged rigging took place at major tournaments including Wimbledon and the French Open. All the players were allowed to continue competing.
The match-fixing was allegedly orchestrated by gambling syndicates in Russia and Italy and involved prominent players. It is suggested that players are being targeted in hotel rooms at major tournaments and offered 50,000 dollars (£35,200) or more per fix by corrupt gamblers. The syndicates have made hundreds of thousands of pounds placing bets on scores of matches, according to the investigation.
It is claimed the referrals to the TIU, set up to police the sport, were prompted by an investigation which started in 2007 following an inquiry into suspicious betting patterns in a match between Nikolay Davydenko and Martin Vassallo Arguello. Both men were cleared of breaking any rules.
Despite an increasing amount of evidence of suspicious activity revolving around a significant number of top players, no sanctions were handed out and the investigation was officially shelved the following year.
Betting investigator Mark Phillips believes the findings of the original 2007 inquiry should have been followed up and acted upon by the relevant authorities.
He told the BBC: "Evidence that we gathered ... we believed was very strong. There was a group of between six and 10 players really who were the main focus of the evidence that we dug up.
"We believed they (the TIU) would carry on the investigations from where we had taken them; we had done a lot of work on the investigation and certainly the betting investigations were a long way down the road.
"As far as we know, nothing happened with the evidence that we presented. Certainly none of the players that we had concerns about faced disciplinary action from the TIU in the next year or two."
Association of Tennis Professionals president Chris Kermode strongly denied that the TIU, which was set up as an independent body by the sport's various governing bodies, was deliberately seeking to hide any suspected improprieties.
"I can assure you that tennis is not treating this lightly," he said, while Nigel Willerton, who leads the TIU, insisted that the sport took a "zero-tolerance approach to all aspects of betting-related corruption".
Among the allegations is the claim that winners of singles and doubles titles at Grand Slam tournaments are among the core group of 16 players who have repeatedly been reported for losing games when highly-suspicious bets have been placed against them.
It is also suggested that the names of more than 70 players appear on nine leaked lists of suspected fixers who have been flagged up to the tennis authorities over the past decade without being sanctioned.
Mr Kermode, who believes the threat of sports match-fixing is at an "incredibly small level", told the BBC: "It is simply not true that we are sitting on evidence.
"What happens is that information and intelligence are given to the Tennis Integrity Unit and they then have to turn that into evidence.
"There is a big difference here between information and intelligence as to evidence. Every single bit of information that the Tennis Integrity Unit receives is investigated properly."
World number two Andy Murray tweeted a link to the Buzzfeed report on Sunday evening.
Building on the initial dossier of evidence, Buzzfeed News claims to have devised an algorithm which analysed gambling on professional tennis matches over the last seven years.
The organisation said its results identified 15 players who regularly featured in matches involving unusually lopsided betting patterns. Furthermore, four of those players lost almost all of those matches concerned, at a probability of around 1,000 to one.