Pastor Maldonado declared that Williams has taken a huge step backwards this season after being eliminated from Australian Grand Prix qualifying in Q1.
Maldonado had been delighted with the form of the 2013 Williams after its initial tests, but the car has been off the pace in Melbourne so far.
Although his team-mate Valtteri Bottas made it through to the currently-delayed Q2 in 14th place, Maldonado could only manage 17th.
"I think we're back to the condition of two years ago in the team," said Maldonado.
"We need to work very hard to solve the problems.
"The car is undriveable at the moment and we need to work. That's it."
Maldonado believes the main issue is Williams failing to get the right set-up for the Albert Park track.
"For whatever reason, we didn't adapt our car to this track, whatever the conditions," he said.
"In the wet we were slow, in the dry as well."
The Venezuelan is slightly more optimistic about his race prospects.
"The pace for tomorrow seems to be much better but qualifying pace is really bad," Maldonado said.
AUTOSPORT Australian GP coverage:
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