The Venezuelan, who won the Spanish Grand Prix from pole position last year, said the Williams team was back in the same state as in his rookie season in 2011, their worst in 35 years in the sport.
The 28-year-old will start in 17th place on the grid for Sunday's season-opening race among the rookie drivers with the places above him yet to be decided after the rain prevented the completion of qualifying.
"I think we are back to two years ago (with the) conditions in the team," he told TV reporters. "We need to work very hard to solve the problems. The car is undriveable at the moment.
"We need to work. That's it ... for whatever reason we did not adapt our car to this track. In whatever conditions.
"In the wet we were slow and in the dry as well. We'll see. The pace for tomorrow seems to be much better but qualifying pace is really bad."
Maldonado scored 45 of his team's 76 points last season as the former champions Williams finished eighth overall, his win in Barcelona giving them a first victory in nearly eight years.
He also developed a reputation for getting into trouble with the stewards, however, and racked up a string of penalties that he was determined to stamp out this season.
To add to his embarrasment on Saturday, his team mate Valtteri Bottas was the only rookie to make it through to the second round of qualifying in the other Williams with the 15th quickest time of the session.
The heavy rain means the Finn will have to wait until Sunday morning to find out exactly where he will start on the grid but he was relieved to have survived sometimes treacherous conditions at Albert Park.
"That was interesting indeed! Not the easiest condition for my first qualifying.. will continue tomorrow!," he tweeted.