The 21-year-old, who has made the No.9 shirt his own since his try-scoring full debut in the 21-20 defeat of Australia in Sydney and played an important role in England’s Six Nations triumph, has undergone keyhole surgery on his left knee.

Youngs, who deposed Harlequins’ Danny Care as England’s first-choice scrum-half, is expected to be out for six weeks but could return for England’s final two World Cup warm-up matches.

Care is likely to step into Youngs’ boots, while Saracens’ Richard Wigglesworth and Wasps’ Joe Simpson are also part of Martin Johnson’s initial 45-man training squad.

A Rugby Football Union statement said: “Ben will continue his rehabilitation with the England medics in consultation with their Leicester counterparts.

“A full recovery is expected as quickly and as safely as possible.”

Youngs is scheduled to return just as Martin Johnson whittles his squad down from 45 to 30 but as long as he returns to fitness he will be expected to make the plane to New Zealand.