Some Hollywood actresses are cautious about revealing too much skin but 20-year-old Scarlett Johansson had to be persuaded to keep her underwear on, said her director in The Island, Michael Bay.

Speaking before the New York premiere of the thriller, which stars Johansson and Ewan McGregor as human clones on the run, Bay said he was prepared for the usual actress nerves when it came to shooting a love scene between the two leads.

"We're ready to go and of course the actress is not there," he told reporters. He said he was summoned to Johansson's trailer, expecting to have to reassure the star of Lost in Translation that her privacy and dignity would be protected.