Iron Man has held on to the number one spot in the North American box office as the summer blockbuster season endures.

The comic book adaptation added $50.5 million (£25.8 million) to its opening week haul, making producer Paramount $177.1 million (£90.4 million) in a fortnight.

Iron Man, starring Robert Downey Jr and Gwyneth Paltrow, pushed Speed Racer, from the Wachowski brothers, and rom-com What Happens in Vegas into second and third, Screen International reports.

Speed Racer, based on the 1960s anime of the same name, made just $20.2 million (£10.3 million), with the Ashton Kutcher- and Cameron Diaz-starring What Happens in Vegas taking $20 million (£10.2 million).

But despite the disappointing returns of the second and third biggest films, the box office was still up 21 per cent on the corresponding weekend last year.

Next week's biggest release is The Chronicles of Narnia: Prince Caspian, with Walt Disney and Buena Vista pinning their summer hopes on the fantasy sequel.

North American box office top ten (Last week's position)

1 Iron Man (1)
2 Speed Racer (new entry)
3 What Happens in Vegas (new entry)
4 Made Of Honor (2)
5 Baby Mama (3)
6 Forgetting Sarah Marshall (5)
7 Harold And Kumar Escape From Guantanamo Bay (4)
8 The Forbidden Kingdom (6)
9 Nim's Island (7)
10 Redbelt (41)

12/05/2008 12:06:48