High hopes: The contestants enter the house in July

But the group - who are living under surveillance in a house in a Hollywood studio complex - turned down the offer.

Producers had wanted to introduce a new contestant into the house - an "opinionated" 22-year-old who said others called her "a bitch".

Megaphone

Their plans were scuppered when a woman stood outside the walls of the Big Brother set and warned the contestants with a megaphone that the plan was coming and that it was a trick.

This prepared them for when the show's host, Julie Chen, announced a suitcase containing $20,000 (�13,800) in cash was available for anyone who would walk out.

One contestant - Eddie from Long Island, New York - scoffed: "That's a night at the bar for me."

A second case was added to the offer, containing $30,000 (�20,700) - but there were still no takers. "Congratulations on your resolve," Chen said, clearly disappointed.

Jean Jordan: Her eviction was a highlight of the US show

Viewers had earlier seen the woman who would have entered the house - 22-year-old Beth, who was shown wearing a tiny bikini in a short film.

"I'm opinionated, and sometimes that's misconstrued as being a bitch," she said.

But after finding out she couldn't enter the house, she said the contestants were "insane" not to take the bribe.

Ratings drop

Ratings for Big Brother started well but have fallen over time following the evictions of former topless dancer Jean Jordan and youth counsellor William Collins - who turned out to be a field marshal for the New Black Panther Party.

It has also suffered badly in comparison with Survivor - which preceded it on Wednesdays.

While Survivor, which was set on a desert island, became a national obsession and attracted over 50 million viewers for its finale, Big Brother was dubbed "excruciating" by critics and attracted 11 million viewers last week, slipping out of the top 10rankings.

Screenwriter Caleb Wilson with his Big Brother missile

The show's security was also breached earlier in the series when two publicity-seeking screenwriters threw a tennis ball stuffed with fake news stories - including one in which President Clinton purportedly called Big Brother a "national disgrace" - into the house's garden after finding it was unguarded.

The set was also buzzed by a plane towing a banner reading: "Big Brother is worse than you think. Get out now."

The company behind the show, Orwell Productions, also faces legal action from the holders of the film rights to the novel 1984 - which gave the show its name.

The show's winner will be chosen on 30 September, over 12 weeks after the contestants entered the house.

By contrast, the UK version ends on 15 September - after just nine weeks.