Jacque is a former 250cc world champion

The Frenchman will be staying on with the Japanese team to help develop their race bike under contract until 2008.

He said: "My repeated injuries this year have forced me to retire. I'll do my best to develop the bike to help Kawasaki reach the highest level."

The 33-year-old's latest crash came at the Catalunya Grand Prix on 10 June.

"My body keeps telling me maybe it's time to move on and I don't feel competitive enough to ride at the top level," he said.

Ichiro Yoda, Kawasaki's race director, said: "We held talks after his (Jacque's) fall in Spain.

"I asked him to end his career and offered him the job of becoming our development test rider up to the end of 2008.

"We're counting greatly on him to improve the bike."

West, 25, has bought out his World Supersport contract with Yamaha to join Kawasaki.

He tested for Kawasaki in Barcelona last week and will make his debut for the team at this weekend's British Grand Prix.