Ryan Reynolds and Sandra Bullocks in a scene from 'The Proposal'

The film, co-starring Ryan Reynolds, marks Bullock's biggest opening weekend ever, and finished way ahead of studio expectations.

Sleeper summer hit The Hangover slipped to second place, but passed the $150 million (£100 million) mark in its third weekend on release.

Disney/Pixar's Up took in over $21 million (£14 million) in its fourth weekend, taking its tally to $224 million (£149.3 million), and Jack Black's caveman comedy Year One debuted in fourth place with a respectable $20.2 million (£13.4 million).

Source: WENN