The Williams team is planning to use KERS in next year's car, despite the Formula One Teams' Association having agreed to drop the system voluntarily.
FOTA teams announced in June that they would not be using KERS in 2010 as they deemed the technology, used by a minority of squad this year, was too expensive.
The pact, however, could now collapse, with Williams having confirmed it is continuing with the development of its KERS with the intention of using it in next year's car.
"We fully support the use of KERS and always have done," Williams technical director Sam Michael said on Tuesday.
"Given the environmental and sustainability pressures that Formula 1 is going to face in the future, KERS is a positive step for the sport.
"It's in next year's regulations, so we're continuing developing our system with a view to using it on next year's FW32."
Williams, developing a flywheel-based KERS, has not used the system this season.
The Grove team recently rejoined FOTA after it was suspended earlier this year when it broke ranks with the rest of FOTA and entered the 2010 world championship before the FIA's initial deadline.
Only McLaren and Ferrari have been using KERS regularly this year.