Williams fear Formula One champions Ferrari could spring a nasty surprise on their rivals this season.
"It's a fantastic team, they almost never make a mistake," said Frank Williams. "What worries me deeply is Ferrari's announcing not that long ago, that 'we'll make a new car for April again'.
"They have obviously, I'd imagine, travelled along the path we've all travelled along with the new aerodynamic rules and said we need to be clever and more inventive than this.
"I'm just worried that they may have thought of something very, very clever and thought it's worth having a fresh start to get the best out of this. I hope I'm wrong."
Ferrari have won the last six constructors' championships in a row and dominated the 2004 season by taking 15 of the 18 races. Germany's Michael Schumacher, collecting his seventh title, won 13 of them.
The Italian team's technical director Rory Byrne said in November they would start the new season with an interim version of their 2005 car.
"The aim is to have the new car on track at the end of February," he said at the time.
"We could bring it out from the first race of 2005 but we are not in such a hurry because we want to go deeper into research and design so that it is almost perfect when it does make its debut.
"The new car will represent another big step forward."
Ferrari also stand to benefit from their refusal to limit testing while the other nine teams have agreed to restrict theirs to cut costs.
Williams said he hoped that Ferrari could eventually be shamed into line.
"If the teams are prepared to take some pain and do less testing and leave Ferrari out there then we hope that you guys, especially the Italian press, will start to moan at them.
"We are resolved. No gain without pain. The teams are desperately serious about saving money."