Lance Armstrong says he has nothing to worry about "on any level" over new doping allegations raised in a report by Sports Illustrated.

The seven-time Tour de France winner curtly brushed aside questions about the story today before taking part in the second stage of the Tour Down Under.

The story challenged Armstrong's statements that he cut ties to an Italian doctor and training adviser who has long been accused of helping cyclists cheat.

Armstrong repeatedly refused to comment on the report before saying he had perused it. "I have nothing to worry about on any level," he said.

Johan Bruyneel, Armstrong's mentor and the manager of this RadioShack team, also refused to discuss the report.

Without naming its source, Sports Illustrated said that when Italian authorities raided the home of Armstrong's team-mate Yaroslav Popovych last November in Italy, they found texts and emails linking the RadioShack team with Dr Michele Ferrari as recently as 2009.

Armstrong severed his connection with Ferrari in 2004, amid accusations the doctor aided another rider in using performance-enhancing drugs. Ferrari was convicted and then later cleared of criminal charges on appeal.

The Armstrong spokesman, Mark Fabiani, called the report "old news from the same old, discredited sources".

A US federal grand jury in Los Angeles has been hearing evidence for months on cheating in professional cycling. The investigation turned toward Armstrong – and several of his associates have testified before the panel – since his former team-mate Floyd Landis accused the seven-time Tour de France winner of systematic doping.

Armstrong won the Tour de France every year from 1999 to 2005. He's currently competing in the Tour Down Under, which he says will be his last race outside the United States.

Armstrong has never tested positive for a performance-enhancing substance.