Playboy Playmate Karissa Shannon has threatened to sue Celebrity Big Brother after actress Denise Welch pulled down her pyjama bottoms.

The incident, which occurred as the pair were dancing on a sofa during a boozy party on the Channel 5 show.

Karissa was outraged at having her bottom exposed, and she stormed into the diary room to warn that she would take legal action.

"You're going to show my ass on TV, that's for sure.

"I'm not cool with that so I'm going to sue you guys. My management's not going to be ok with this."

She added that she was "done" with X Factor flop Frankie Cocozza's "sexual harassment".

Welch, who last week went topless during a hot tub session in the house, claimed she did not realise her actions would have offended Karissa.

"It's your great bum, show it off," she said.

But the Playboy star declared: "I do not pull my pants down for anyone."

Her twin sister, Kristina, later added: "Everybody knows she's a really reserved person."

Former glamour model Nicola McLean was involved in a noisy row with Welch, and then yelled to Big Brother that she wanted to leave the house.

The show's winner will be revealed on Friday night.