Despite not failing a drugs test, the 50-year-old admitted to Sports Illustrated that he had used the spray, which contains small amounts of the IGF-1 hormone that features on the World Anti-Doping Agency (WADA) list of banned substances.

Singh was subsequently sanctioned with a 90-day ban by the PGA Tour, who referred the case to WADA following an appeal from the golfer, which was successful.

The PGA Tour had warned players of using the spray in 2011, but the Tour decided not to take further action against Singh following correspondence with WADA last month.

"I am proud of my achievement, my work ethic and the way I live my life," said Singh in a statement.

"The PGA Tour not only treated me unfairly, but displayed a lack of professionalism that should concern every professional golfer and fan of the game."

The lawsuit filed by Singh reads: "Singh seeks damages for the PGA Tour's reckless administration and implementation of its Anti-Doping Program (sic).

Singh's attorney claims that the PGA Tour opened his client to "public humiliation and ridicule" with their handling of the deer antler spray saga

"After exposing Singh, one of the PGA Tour's most respected and hardest working golfers, to public humiliation and ridicule for months, and forcing Singh to perform the type of scientific analyses and review that the PGA Tour was responsible for performing, the PGA Tour finally admitted that the grounds on which it sought to impose discipline were specious and unsupportable."

His attorney, Peter R. Ginsberg, released a statement which accused the Tour of unfairly accusing the three-time Major winner of cheating.

"The PGA Tour could have known by conducting some basic testing and research," said Ginsberg

"The product that Singh sprayed contained no active biological ingredient and could not possibly have provided any performance enhancement,"

"The PGA Tour has now finally admitted that the use of deer antler spray is not prohibited.

"Rather than performing its duties to golfers first, and then determining whether there had been any violation of the anti-doping program, the PGA Tour rushed to judgment and accused one of the world's hardest working and most dedicated golfers of violating the rules of the game."

The PGA Tour are yet to acknowledge the lawsuit publicly, and Ty Votaw, the PGA Tour's executive vice-president of communications and international affairs, told Reuters: "We have not seen the lawsuit, just the statement.

"We have no comment."

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