The glamour model said she would be unhappy to see Giggs in the Channel 5 reality show, as she objects to the 29-year-old finding fame through her eight-year affair with ex-brother-in-law Ryan Giggs.
"'I know we all have difficult lives, but I can't work out how things went so wrong that she did what she did," McLean told New. "If she goes on the show, she is just making money from ruining people's lives. I know everyone has a past but, to me, it's the lowest of the low."
Giggs hit back at McLean's comments on her Twitter profile by saying: "Someone who spends their life commenting on and judging others lives is what I call a BUSY ARSE with no life of their own to talk about!
"She def needs to #getoverit n get a hobby.. Mind u, she needs to have something to talk about and she obviously has nothin else to say that is of interest to anyone!!"
Giggs denied rumours linking her to Celebrity Big Brother back in December. She is believed to have been offered a £50,000 fee to appear.
Ruby Wax, X Factor star Frankie Cocozza, Denise Welch and TOWIE's Kirk Norcross are among those tipped to enter the Elstree compound.
Celebrity Big Brother launches Thursday (January 5) at 9pm on Channel 5.
> Natasha Giggs on Ryan Giggs affair: 'It was always going to end badly'
> Celebrity Big Brother 2012: See inside the new house in pictures
Watch Brian Dowling, Amy Childs, Jedward and Kerry Katona in a Celebrity Big Brother trailer below: