Tom Boardman has split with the AmD Tuning British Touring Car Championship team, which is now looking for a replacement driver to complete the season.
Boardman, a race winner in 2011, rejoined the BTCC after a six-year break to race one of AmD's ex-works MG6 GT machines alongside Scot Rory Butcher.
The Lancastrian finished fourth in the rain-affected second round of the championship at Brands Hatch but has only featured in the top 15 on one other occasion, meaning he is 27th in the standings.
"It is always a difficult decision to make changes to any of our team personnel but the long-term aims and goals of the team must come first," said AmD Tuning boss Shaun Hollamby.
"We will be replacing Tom Boardman for the second half of the BTCC. I would like to thank Tom for his efforts this year and wish him luck with his future motorsport."
Hollamby said he was in contact with possible replacement drivers and a decision would be made by the end of the month.
Boardman said he was not aware of the decision and it had come as a shock.
"The first I knew about this was when I read it on social media and I was very disappointed," said Boardman.
"My results were varied in the first half of the season having had problems with the car's set-up in qualifying.
"The fact that I am actually leading the Forever Forward standings [a Dunlop-backed award for the most positions gained in a race] surely shows my racing abilities are very much alive.
"However, if this is AmD's decision so let it be.
"I'm sure I will live to fight another day even if this may be next season now.
"I will finish off by thanking the AmD team for giving me the opportunity to race the MG in the BTCC and wish them well for the rest of the season."
AmD, which also runs a brace of Audi S3 saloons for Ollie Jackson and Sam Smelt, will be present at the official BTCC TOCA tyre test at Snetterton on Wednesday and Thursday next week.
The team is required to find a driver to run in the second half of the season under the terms of its TOCA BTCC licence, which all entrants must have.