Filming began last week on the project, which has aroused protests and legal action over fears that the shoot will damage its tropical island location.

David Willis: Protests no match for Hollywood

Environmentalists and local people opposed to the filming say it will ruin the picturesque bay, which lies in a national park on Phi Phi Island.

DiCaprio plays a young traveller who stumbles across a mysterious island in Thailand inhabited by a group of backpackers.

The 24-year-old actor has issued a press statement, in which he insists: "I've seen extraordinary measures being taken to protect the island.

DiCaprio: Pledged to protect beach

"I pledge to remain vigilant and tolerate nothing less. I love Thailand and I feel privileged to be filming here."

Protestors have gone to great lengths to bring their message to the Titanic star. One group on Saturday were based in a motor launch moored offshore from his hotel, bearing a sign reading "Don't Rape Our Beach."

Thai newspapers are saturated with gossip about the actor, reporting last week that a Thai masseuse has gone into hiding to avoid being hounding by local reporters after she gave DiCaprio a traditional Thai massage.

Beach sealed off

Production company 20th Century Fox has secured permission from conservation officials to seal off the beach for six weeks, and is employing security guards against any attempts to disrupt the shoot.

A court case is pending against Fox and against the Thai officials who authorised the shoot, but filming has been permitted to proceed before the case goes to court in March.

The beach is being cordoned off for six weeks

Environmentalists bringing the legal case allege that the filming contravenes legislation protecting national parks.

Sit-ins on the beach and a letter-writing campaign in the Thai press have marked months of controversy over the film plans.

The location boasts natural white sand and a natural amphitheatre of limestone cliffs, but filmmakers have uprooted bushes and planted coconut trees on the bay, to make it match a Hollywood image of a paradise island.

There are also reports that whole sand dunes have been moved for the shoot, but producer Andrew Macdonald said the dunes had been damaged by the sea.

"We honestly believe we are making some temporary changes to environment but it will not damage it in the long run," Mr Macdonald said.

Opponents of the shoot argue that the damage will be irreversible.

"This is not filmmaking - this is power," countered environmentalist Kanjana Vanit.