Olympic champion Rebecca Romero will not compete at next year's London Games following the announcement that she has left Great Britain's cycling team.
The 31-year-old Englishwoman has rarely competed on the track since winning gold in the individual pursuit in Beijing three years ago.
Romero only took up cycling in 2006, having already won a silver medal in rowing at the 2004 Games in Athens.
She was the first Briton to win medals in two sports at a summer Olympics.
"Having suffered several setbacks at crucial points, I believe I'm no longer on a pathway which will see me fulfil my Olympic ambition to win a second Olympic gold medal," said Romero.
"I'm proud to have contributed to the cycling team's great Olympic triumph in Beijing and I thank all the amazing people within British Cycling who were central to my success.
"I wish my current team-mates every success in London next year."
Romero had been unhappy at changes made to Olympic cycling in 2009 that saw her event removed from the programme for 2012, forcing her to aim for selection to the team pursuit line-up.
Injury forced Romero to miss the World Cup event in Manchester in February, and she was again absent when Wendy Houvenaghel, Laura Trott and Dani King won team pursuit gold for Britain at the World Championships a month later.
Romero's first Olympic medal came in rowing, as part of Britain's quadruple scull, which won silver at the Athens Games, and she was awarded an MBE in 2009 for her achievements.
British Cycling performance manager Shane Sutton said: "Rebecca's decision to leave is a great loss to the team and it's a shame to lose an Olympic champion going into the Olympic year.
"Looking ahead, we have some great young talent in addition to experienced riders in the team pursuit squad and I'm confident we can remain on track to hit our performance targets in the lead up to and during the London Olympic Games."