Gary Player has claimed some golfers are taking performance-enhancing drugs to boost their game and wants random testing brought in as soon as possible.
Player, 71, has won nine majors
"I know for a fact that some golfers are doing it," said the South African, who won nine majors in his career.
"I would say there are 10 guys taking something. I might be way out. It's definitely not going to be lower, it might be a hell of a lot more."
Player, 71, says two players have told him personally they are taking drugs.
He refused to reveal who they were but said he could see a big physical change in one of those he had spoken to.
"One guy told me - and I took an oath prior to him telling me - but he told me what he did and I could see this massive change in him," said Player.
"And somebody else told me something I also promised I wouldn't tell, that verified others had done it."
Player also revealed he had himself rejected offers from doctors to take Human Growth Hormone (HGH).
"Every doctor I go to, without fail, says 'Gary, you must take HGH'," he explained.
"He said it will make you stronger, your skin will be thicker because your skin starts to get scaly, your hair is stronger, your complexion will be better, you'll be more supple.
"He said you'll start hitting the ball 20 to 30 yards further.
"I said I've done everything I wanted to do in golf. I've got 20 grandchildren, I want to enjoy my life with them and I don't want to take it because I'm not sure what it will do to me."
Golf is in the process of formulating a drug testing policy as it attempts to fall in line with other sports.
The PGA Tour is drawing up a list of prohibited substances while the European Tour says it plans to have a drugs policy in place by January 2008.
The LPGA Tour has also said it will start drug testing in 2008.
Meanwhile, Open organisers have said the tournament will eventually become part of an overall random testing system.
I know some guys have taken Medrol packs for inflammation in their wrists, but, other than that, I really don't see anybody doing anything
"We are working closely with the Tours around the world to achieve the introduction of a uniform drug-testing policy," said Royal & Ancient Club chief executive Peter Dawson.
"Those discussions, I'm pleased to say, are at a pretty advanced stage."
Some testing has already been carried out.
The International Golf Federation tested 12 golfers at the World Amateur Team Championships in South Africa last year. There were no positive findings.
Four years ago at the French Open, the government decided to test some players on the final day.
France's Marc Farry sample was found to contained the banned steroid prednisolone, an anti-inflammatory not considered performance-enhancing.
But he was subsequently exonerated because the substance was prescribed by a doctor to combat a wrist injury.
Asked if he thought drugs testing was needed in golf, Player responded: "It is absolutely essential."
He also warned that performance-enhancing drugs were a real threat to the game.
"We're dreaming if we think it is not going to come into golf," said the three-times Open champion.
We'd be wise to determine a policy, enter a period of education and then go for it full throttle
World number one Tiger Woods, who has come out in favour of drug testing, was asked on Tuesday if he would be surprised if a golfer tested positive.
"If anything, probably out here it would be testing positive for maybe being hung over a little bit," he said.
"But that's about it. I know some guys have taken Medrol packs for inflammation in their wrists, but, other than that, I really don't see anybody doing anything, or have heard anybody doing anything."
Phil Mickelson also said he thought golfers were clean and said he did not think there was "even a remote chance" that a golfer would test positive for steroids.
Dawson said once a drug-testing policy was agreed there should be a period of player education, maybe lasting a year.
"We'd be wise to determine a policy, enter a period of education and then go for it full throttle," he said.
"What I do support is getting on with this in a measured, but quick fashion."