The Reservoir Dogs actor, who had an ongoing spat with Welch during their time on the Channel 5 reality show, claimed that Welch's behaviour in the house made him "sick to the stomach".
"She offered to sleep with me a number of times - she just kept trying," Madsen told the Daily Star Sunday.
"I couldn't understand why she was pressing me to do that. But she was deadly serious. I know quite a bit about women and I know when a girl is being serious - and she definitely wanted it to happen. It made me sick to my stomach - the idea repulsed me. If I was stranded on a desert island I would rather f**k a coconut tree."
Madsen also responded to Welch's husband Tim Healy's threats to "sort him out", arguing that the British actor was probably "pretty embarrassed" by his partner's behaviour on the show.
"I feel sorry for her husband. I heard he wants to 'sort me out'. Well here I am," said Madsen. "But if he wants to sort something out perhaps he should have a chat with his wife."
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