The sport's governing body in England, the Rugby Football Union, launched an investigation yesterday after allegations in the News of the World. Mr Dellaglio, who has been away for the weekend with his family, was consulting advisers over the matter last night.
The claims, apparently based on comments made by the player to an undercover female reporter, come days before he is due to fly to Australia with the England squad preparing for the rugby world cup later this year. Rugby experts said yesterday that if the allegations were true, it was difficult to see how Mr Dellaglio could retain a place in the team, let alone the captaincy.
Mr Dellaglio, 26, is said to have told the paper he used to deal in cocaine before he took up rugby. "I used to be a drugs dealer. I made big, big money from dealing in drugs," he is alleged to have said.
But perhaps the most serious charge made by the paper is that Mr Dellaglio told the reporter he had celebrated the victorious 1997 Lions tour of South Africa by taking ecstasy with two colleagues. "We got absolutely mullered," the paper quoted him as saying.
If true, the allegations represent one of the biggest scandals to have hit rugby union: as captain Mr Dellaglio is central to the England team set-up and is prominent in the sport's promotional activities, especially those aimed at young players. He is believed to earn pounds 200,000 a year from the sport.
Yesterday a brief RFU statement said that Brian Baister, chairman of its management board, and the chief executive, Francis Baron, were discussing the allegations as a "matter of urgency". It added: "The RFU will be speaking to Lawrence Dellaglio as soon as possible before making any further comment."
The men, along with the England coach, Clive Woodward, and international committee chairman, Fran Cotton, were due to meet Mr Dellaglio today.
Yesterday Mr Dellaglio, whose club side, Wasps, won the Tetley's Bitter Cup a week ago, was returning to his London home with his partner, Alice Corbett, and their two young children, the youngest born three weeks ago.
His agent, Ashley Woolfe, said he had spoken briefly to the player. "Lawrence has been away for a few days, and there is nothing I can say at this stage," he said. He would be meeting the player as soon as possible. Mr Woodward, who appointed Mr Dellaglio as World Cup skipper in October, said: "I am not making any comment until I have spoken to Lawrence."
Mr Cotton, manager of the 1997 Lions tour, said he was unaware of any drugs being taken. "All of us responsible for helping England's players during the World Cup will be talking to Lawrence and establishing the facts," he said.
The News of the World is believed to have worked on the story for six weeks. Its reporter met the player several times, most recently in a London hotel last Friday.
Mr Dellaglio is widely considered to be one of English rugby finest talents. He said he committed himself to the sport after his sister Francesca drowned when the Marchioness pleasure boat sank on the River Thames in 1989.