Monster-in-Law has not been well received by the critics

Monster-in-Law, which sees Fonda, 67, play prospective mother-in-law to co-star Jennifer Lopez, took $24m (�13.4m) across the weekend.

Football comedy Kicking & Screaming, starring Robert Duvall and Will Ferrell, entered at number two.

However, neither film lifted Hollywood out of its current box-office slump.

Takings for the past 12 weekends have been down compared with the same period last year.

NORTH AMERICAN BOX OFFICE CHART 1. Monster-in-Law, $24m 2. Kicking & Screaming, $21m 3. Unleashed, $10.6m 4. Kingdom of Heaven (above), $9.6m 5. Crash, $7.2m Friday-Sunday. Source: Exhibitor Relations

However, box office returns were up 21.7 per cent from last weekend.

"I'm encouraged by these numbers," said Paul Dergarabedian, president of box-office tracker Exhibitor Relations.

"As we head into the week of Star Wars, this is definitely a positive-looking marketplace."

This weekend's top 10 contained two other new releases, the martial arts thriller Unleashed, starring Jet Li, at number three, and the psychological thriller Mindhunters, starring Val Kilmer and LL Cool J, at number 10.

Sir Ridley Scott's Kingdom of Heaven fell to number four, after a disappointing opening of just $20m (�11.2m) last weekend.

The slump is expected to end on Thursday when the final Star Wars film, Episode III: Revenge of the Sith, hits screens, kicking off the Memorial Day holiday weekend in the US.

"There's nothing wrong with our business that a good movie won't fix," said David Tuckerman, head of distribution for New Line Cinema, which released Monster-in-Law.

"Star Wars will jump-start us."