Williams has confirmed the exit of Paddy Lowe from the team and its board of directors with immediate effect after the former Technical Director took a leave of absence earlier this season.
The Grove-based team has seen a sharp decline in the performance of their cars after coming off the back of two years where the team finished third in 2014 and 2015, and a further two in fifth in 2016 and 2017.
Williams' 2019 season was hampered by issues through the winter break which saw the team struggle to make pre-season testing in Spain on time, arriving two days late and with parts on the car which were also illegal according to the technical regulations.
Paddy Lowe said: “After a period of careful reflection I have reached the decision that I will not return to work at Williams.“
Claire Williams added: “We understand and respect the decision Paddy has reached and wish him well for the future.
“I wish all my previous colleagues the very best to meet the challenges ahead, which I am sure they will do. I would especially like to thank the Williams fans who are so supportive.”
Lowe previously worked with the team in the early 1990s where he helped with the development of active suspension systems which helped Williams to title glory before being banned at the end of 1993.
After moving to McLaren that year, he rose through the technical ranks before becoming the technical director in 2011, overseeing championships won by Mika Hakkinen and Lewis Hamilton.
Lowe would join Mercedes in 2013 where he would link up with Hamilton again and once again capture title-winning success before moving to Williams at the end of 2016.
In a swap deal with Mercedes, Lowe would move back to his former team and driver Valtteri Bottas would move to the Silver Arrows after World Champion Nico Rosberg had decided to retire at the end of 2016.