Gareth Howell has split with the Motorbase Performance SEAT team.
The former race winner had joined the independent newcomers this year after a part-season with champions Team Halfords. But he had a difficult start to 2007 and is only 13th in the standings, with just a single top five finish.
Team principal Dave Bartrum said the number of incidents that the Motorbase cars had been involved in during the first half of the year had left the team in a difficult position.
"The amount of accident damage we've had so far has put pressure on the budget," Bartrum said.
"The cars have spent a lot of time in the bodyshop and waiting for parts and that has hurt our testing schedule. Our cars have had seven big hits in three weekends, as well as the regular combat damage and it's been tough for everyone."
Motorbase will announced a replacement for Howell before next weekend's Donington Park races.
Bartrum confirmed that Howell's teammate Matt Allison's future was secure.
"We're delighted with Matt's performance and expect he will continue his excellent progress through the second half of the season," he said.
"We will be a two-car team for the rest of 2007 and beyond. In the meantime, we wish Gareth well for the future."