Jonathon Humpries: If anyone was doing drugs, everyone would know about it

Williams, who starred as fullback in Wales' all-conquering 1970s teams, claims he knows of two players in the 1998 Wales side who are taking anabolic steroids.

The former great has added his voice to the growing chorus of disapproval over the prevalence of drugs in rugby union.

A clutch of former internationals, including England's Jonathan Webb and Jeff Probyn and Neil Francis of Ireland, have also raised their concerns about the issue.

"Taking banned substances is fairly rife, and most of it is done in the off-season," Williams said.

JPR was one of the stars of the Lions 1974 triumph in South Africa

"It is fairly well recognised that certain players have been on anabolic steroids and haven't been tested.

"I know of two players in Wales who are still playing, and have played at international level. I have had it confirmed by the two players," he told the Sunday Times.

The Welsh Rugby Union admitted Williams' accusations are likely to prompt a thorough probe.

"JPR's accusations are obviously serious ones, and it does seem strange that he has not voiced his concern directly to the Union," said a WRU spokesman.

"The innuendo leaves an unsatisfactory feel about it, and it is now down to the Union to follow through what has been alleged and to ascertain what substance there is to JPR's concern."

Williams' fears were confirmed by former England and British Lions prop Mike Burton, who said: "Drugs are a problem. It is obvious from some of the body shapes you see that they are not natural."

The latest claims come just weeks after the Irish Rugby Football Union was rocked by allegations from their former international second row forward Neil Francis that un-named top Irish players had regularly taken drugs.

As a result of Francis' revelations, and a subsequent drug testing report from the UK Sports Council, a tribunal will investigate cases of two players.