The former Tour de France champion Jan Ullrich has announced his retirement from competitive cycling, eight months after his career was put on hold by a doping investigation. The 33-year-old German, who won the sport's most prestigious race in 1997, said at a presentation on Monday (February 26) in Hamburg he would work as an adviser to the small Austrian Volksbank team in order to stay involved in the sport, but was ending his active participation in it. "I would like to repeat officially, that I am ending my active career today," said Ullrich, who has strongly denied any involvement in doping. "It wasn't easy for me, but when you have acknowledged what comes after it, when you have acknowledged, and when your inner voice says 'ok, it's time', then you listen, and it is certainly difficult for me, but it won't break me and I am looking forward to the future." Ullrich was withdrawn from the T-Mobile team just before the 2006 Tour de France after being linked with the Operation Puerta doping investigation in Spain. He was suspended and then dropped by his team despite his insistence that he was not involved. Since then he has been without a place on a professional team, although he has not been charged with a doping offence. Aside from the Tour de France, Ullrich won the Tour of Spain in 1999 and two medals at the Sydney Olympics -- gold in the road race and silver in the time trial. Ullrich was only 23 when he won the Tour in 1997 and many predicted he would go on to dominate the sport in the manner of five-times champion Miguel Indurain, whose reign had ended the previous year. He suffered injury problems in 1998, however, and had to settle for second place in the Tour behind Marco Pantani. Ullrich was unfortunate to spend most of the rest of his career trying to catch seven-times winner Lance Armstrong, while never quite seeming to be at full fitness himself. The German finished second to the American in 2000, 2001 and 2003 and made it on to the podium once more in third place in 2005. With Armstrong retired, Ullrich would have been a strong candidate in 2006 had the Puerta investigation not prevented from from racing. In May last year, Spain's Civil Guard raided Spanish addresses and found anabolic steroids, blood transfusion equipment, dozens of bags of frozen blood and documents listing some 200 professional athletes, including cyclists, who police said were suspected of receiving illegal doping products and treatment from a Spanish doctor. An investigation by a Bonn prosecuting attorney is still active and earlier this month Ullrich provided a DNA sample so that it could be compared with material from Spain.