Zara Phillips will be denied the opportunity to follow in the footsteps of her mother, the Princess Royal, by competing for Great Britain at the Olympic Games after her horse suffered an injury.

The Queen's eldest granddaughter, who was world three-day event champion in 2006 and won the European title in 2005, has withdrawn from the Britain equestrian team for the Beijing Games in August. Toytown, her 15-year-old horse, suffered a soft-tissue leg injury during training in Gloucestershire that dashed Phillips's hopes of adding an Olympic gold medal to her world and European titles.

It is the second such disappointment for the 27-year-old, who was ruled out of the Athens Games four years ago for the same reason, albeit a different injury. The decision to stick with Toytown, a horse she has owned since he was 7, was always risky, according to experts, given his age and injury record. There had been concerns about his ability to deal with the hot and humid conditions in Hong Kong, where the three-day event is being staged from August 9 to 12.

While helping the Britain team to their seventh consecutive gold medal at the 2007 European Eventing Championships in Pratoni del Vivaro, Italy, Toytown stopped suddenly at a fence in the showjumping, ending his owner's prospect of back-to-back individual golds.

Phillips had been geared up for the Beijing Games, but in recent interviews had made almost prophetic allusions to the unpredictable nature of her sport and her chances of success at her first Olympics. “There's still a long way to go, we've got to get there first,” she said on Monday

Yesterday she issued a typically straightforward statement, downplaying the unfortunate turn of events. “I am very disappointed not to have the opportunity to ride at the Olympic Games and feel that Toytown deserved his chance to go,” she said. “However, with horses these things happen and we still have a very strong team. I wish them every success.”

While Olympic officials recognise that they have lost a star attraction, the withdrawal of Phillips is not expected to dent the five-strong team's medal hopes. Yogi Breisner, the team trainer, is aiming to win a team gold, the individual gold, a silver and a bronze. In Athens, eventing brought Britain an individual gold through Leslie Law, a team silver and a bronze for Pippa Funnell.

Will Connell, the equestrian team leader, said: “The British team are saddened by the news, especially for Zara and her team. We have a strong team of reserves and the team are now focused on trying to win medals.”

The British Olympic Association (BOA) will select a replacement rider and horse after a nomination from the British Equestrian Federation. Riders and horses must qualify for the Olympics as a combination.

Colin Moynihan, the BOA chairman, said: “Zara will be devastated. The Olympics are the pinnacle of any great athlete's ambitions and a great deal of hard work has gone into getting there.”

Phillips, who won the BBC Sports Personality of the Year award after her world success, comes from a strong line of competitive riders, but the Olympics was missing from her list of accomplishments. The Princess Royal, who is a member of the IOC, competed in the 1976 Olympics in Montreal after winning the European title in 1971. She was the first member of the British Royal family to appear at the Games, and she completed the Olympic course with concussion after falling on her head.

Zara's father, Captain Mark Phillips, won a gold medal in the three-day team event at the 1972 Games in Munich and coaches the United States team.