Sergey Sirotkin’s Formula 1 backer SMP Racing claims it decided to split with Williams due to the team’s poor performance and lack of development throughout 2018.

Sirotkin has endured a difficult rookie F1 campaign amid a torrid season for Williams, with the British squad announcing on Thursday ahead of the Abu Dhabi Grand Prix that the Russian will be replaced at the team by Robert Kubica from 2019, who will partner Formula 2 championship leader and Mercedes-backed George Russell.

SMP responded to the news by saying it made the call to leave Williams.

F1 2018 Car Comparison

"We decided not to participate in the Formula 1 world championships in a joint project with the Williams Martini Racing team," said founder and head of the SMP Racing programme, Boris Rotenberg.

“We were unpleasantly surprised by the level at which the team was at the beginning of the season. The progress of the car was also not high enough.

“Despite this, Sergey spent a good season in the conditions in which he found himself, gave his 100% and fully completed the tasks assigned to him.

“We are pleased with his work and are currently considering various options for continuing Sergey’s career going forward.

“He will definitely spend a lot of races in the SMP Racing. We will announce our decision soon.”

Sirotkin scored just one point for Williams following Romain Grosjean’s disqualification at the Italian Grand Prix but has matched teammate Lance Stroll for much of the year, with the team languishing at the bottom of the 2018 constructors’ standings.

While Sirotkin confirmed he will not be competing in F1 next year, his career options could include a foray into the World Endurance Championship SMP competes in as part of its LMP1 programme.

"Unfortunately I will not be competing in Formula 1 next year," Sirotkin said in a post on social media.

"It was a very long and difficult year, and not everything turned out the way I wanted it to. But I kept working, put all my effort and my soul into achieving the merited results.

"And, to be honest, I believe that given the circumstances we have done a respectable job."

Deputy team principal Claire Williams added: "To talk about Lance [Stroll] and Sergey, they have done a great job for us this year under what has been really tough circumstances.

“They have both been incredibly professional and have both given everything on and off the racetrack so our thanks at Williams for what they’ve done for the team over the past year or so with us."