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The Celebrity Big Brother 2013 housemates will endure the ‘toughest series ever’ with a ‘dark twist’ planned for launch night, it’s reported.

The Daily Star claims that producers are preparing a ‘string of nasty surprises’ to put the line-up through hell, although details are being kept guarded for the time being.

Meanwhile, the task team are also said to be preparing some of the most challenging tests in Big Brother’s twelve-year history.

An insider said: “Producers want the show to turn nasty for the new series. It’s going to be the house from hell. Celebs will be hoping for an easy ride but bosses have got other ideas.

“Tasks on the first night are usually fun ones but what they’ve got planned this time is horrible. It could completely divide the house and there could be rows starting before the last celeb has even arrived.”

They added: “Every aspect of the show is being tweaked to create plenty of drama. Fans don’t want to see celebs relaxing and having fun, they want to see them under pressure.”

Celebrity Big Brother’s eleventh series kicks off on Thursday at 9pm, with rumoured contestants including Hollywood actress Lindsay Lohan, American reality stars Heidi Montag and Spencer Pratt, and Neighbours actor Ryan Moloney.