Once-great Williams have been in a downward spiral in recent years

Williams co-owner Patrick Head said he was "ashamed" of their performance last year when the once-dominant outfit were eighth in the world championship.

Speaking at the launch of the new Toyota-powered FW29 car on Friday, Head added: "The car is a very good step on where we were last year.

"We are optimistic we can go forward from what was a terrible season."

Team founder Frank Williams added: "Without question, 2006 was not our finest year but I am delighted to see how the entire Williams workforce has pulled together and redoubled its efforts over the winter.

"It is how you perform in adversity that really counts."

606 DEBATE: Will Williams be a force to be reckoned with this season?

Williams have replaced Australian driver Mark Webber, who has joined Red Bull, with the experienced Austrian Alexander Wurz, formerly their test driver.

He is partnered by German Nico Rosberg, who is entering his second year after an intermittently impressive debut season.

There is a really high sense of motivation in the whole team Alexander Wurz

Rosberg said: "Everyone in the team has been very positive and put great effort into the new car, so I think we can be optimistic about a much-improved season ahead of us."

Wurz raced for Benetton in the late 1990s but has spent much of this decade as a test driver and last raced in 2005 as a one-off stand-in at McLaren.

"I have done thousands and thousands of kilometres in the last couple of years, but I haven't had enough of the real stuff - racing. So I can't wait for the season to start," he said.