Russell Coutts, chief executive for the team owned by software billionaire Larry Ellison, said in a statement late on Thursday that unauthorized modifications were made a year ago to its 45-foot catamarans without the knowledge of management. The team will return its prizes and trophies, he said.
An Olympic gold medalist who has won the America's Cup four times, Coutts said the modifications "had no impact on the performance of the boats."
"Our team is very disappointed by this turn of events, and I believe that voluntarily withdrawing from these past AC45 regattas is the appropriate corrective action," he said.
Oracle plans to race a different boat, a 72-foot double-hulled yacht, starting next month in its quest to keep the America's Cup, the world's oldest sporting trophy.
Three teams have challenged Oracle. On Saturday, Italy's Luna Rossa will race against Sweden's Artemis Racing. If Italy wins Saturday's race, it would then race Emirates Team New Zealand to decide who will compete against Oracle.
Meanwhile, an international jury is investigating how weights were inserted into the wrong places on three of Oracle's 45-foot boats, which the team last sailed in April. One of the boats belonged to Ben Ainslie, a four-time Olympic gold medalist who is training alongside the Oracle team for the America's Cup races, which are set to begin September 7.
"As skipper of the boat, I had no knowledge whatsoever that the boat was being raced out of measurement," Ainslie said in an email to the jury. "I am deeply disappointed."
The America's Cup organizers issued a statement saying they, too, were "surprised and disappointed" at the news. Team New Zealand, deemed the favourite of Oracle's challengers, pounced on the news.
"I find it difficult to believe that what we learned last night actually happened at the top level of our sport," managing director Grant Dalton said in a statement on Friday.
Ellison's Oracle team won the cup in 2010 and with it the right to set the rules and choose San Francisco as the venue for this year's competition.
The sailing community has widely criticized Ellison's decision to use high-tech catamarans that can sail as fast as 50 miles an hour on windy San Francisco Bay in light of a May accident that killed Andrew "Bart" Simpson.
The British Olympic gold medalist was trapped beneath the Artemis boat when it capsized during a training exercise.
(Editing by Nick Carey and Ken Wills)
