Willis joined the team in 2001 from Williams

The move comes after Shuhei Nakamoto was promoted above Willis to the new role of senior technical director following a poor start to the season.

"The last five years with the team has been a very challenging but rewarding time for me," said Willis.

"I want to thank all of my colleagues and wish them every success."

Willis' future with Honda looked in doubt when he was placed on "gardening leave" after Nakamoto, formerly Honda Racing Development's engineering director, was promoted in June.

Honda had a dismal start to the season with Jenson Button and Rubens Barrichello collecting only 37 points between them in the opening 12 races.

However at the last race in Hungary, Button claimed his first Grand Prix win while Barrichello finished fourth.

It was the first race Honda had won since it started its partnership with BAR in 2000. The Japanese company took total control of BAR last winter.

"Geoff has made an invaluable technical contribution to the development of our team over the last five years," said Honda chief executive Nick Fry.

"His unwavering focus on the quality of our engineering and the introduction of robust engineering processes has provided foundations that will stand the team in good stead for years to come and pave the way for future success.

"I would like to thank Geoff both personally and from all our team. We wish him every success in the future."