Lions skipper Martin Johnson has been warned he could jeopardise England's World Cup chances unless he learns to keep his boots to himself.

The Leicester lock caused an outcry during Saturday's Calcutta Cup clash at Twickenham when he appeared to stand on the throat of Scottish centre John Leslie.

Johnson was yellow-carded by Irish referee David McHugh, which effectively rules out any chance of him being punished further. But the player was condemned in the Scottish media and former international John Jeffrey called for him to be banned for the rest of the season.

It is the third season on the trot that Johnson has been headlined for the wrong reasons and former England prop Jeff Probyn warned of the dire consequences that will follow unless he changes his ways.

Probyn, now 42 and a member of the Rugby Football Union playing committee, once survived an RFU disciplinary inquiry into a stamping incident against Argentina.

He said: "Martin must curb his over-enthusiasm. He must improve his rucking techniques" - coded rugby-speak for `keep your boots off players' heads'. "Martin knows that in a physical, aggressive sport there is a line dividing the acceptable from the unacceptable and he knows from experience that crossing the line can cost England crucial points."

In December 1996 Johnson cost England a try when Jeremy Guscott was strolling over to score against Argentina. In Cardiff, later that season, Johnson was being penalised for foul play as Tim Stimpson was about to touch down.

Last season new England coach Clive Woodward suspended Johnson for one Test match after he had punched New Zealand captain Justin Marshall at Old Trafford in an episode unseen by the match officials.