The model was having a conversation in the house with former Coronation Street star Julie Goodyear when Brand was mentioned, reports the Daily Mail.
"I think he let her down. I think he shagged around," said Lennard of Brand's split from Katy Perry, before admitting that she had turned down spending a night with the comic.
"I met him and I was a bit disappointed. He's the only man in my life that I've ever run away from before consummating," she claimed.
"One afternoon I agreed to go down there and spend the afternoon, and the door opened and he was standing there in these boxer shirts that were soiled. He was strutting round like a peacock but he was more like a dirty pigeon."
Glamour model Rhian Sugden also revealed that she had had a past encounter with Brand and regretted it.
"He has this Lothario image but when you see him it's not what you think," the 25-year-old said.
Earlier in the week, Lennard claimed that "the truth" about her rumoured affair with X Factor judge Simon Cowell "will come out in the end".
Both Sugden and Lennard are up for eviction this week after receiving the most nominations from their fellow housemates. They face a public vote, before one is evicted next Wednesday (August 22).
Celebrity Big Brother continues tonight (August 18) at 9.10pm on Channel 5, with Bit on the Side airing at 10.10pm.
Photo gallery - Celebrity Big Brother day 3:
Copyright: Channel 5