The ex-Conservative MP, who stepped down from her Northamptonshire constituency in August, said that people who read her column in The Sun know her thoughts about politicians on the show.
"Ugh.#NoThanks," she said on Twitter. "Nothing sadder than a politician, or ex-politician, on any of those shows.
"Just imagining the scene in the whips' office if I said I wanted to skip Parliament for weeks to go on a celebrity TV show. #notpretty."
Of Dorries's claim that she will use the show to publicise her aims to reduce the time limit for abortions, Mensch added: "Nadine pretending that a serious issue like abortion rights is why she did this is the lowest of the low. Indefensible stuff.
"What did she tell the whips, and how much is she being paid? Perhaps whilst in the Jungle Nadine could be set the task of finding the plot. #lostforever."
I'm a Celebrity... Get Me Out of Here! rumoured contestants - photo gallery:
Copyright: Rex Features Richard SakerShe continued: "Good point from another tweeter. Do I recall Nadine commenting about non-MP, non-elected [wife of the Speaker of the Commons John Bercow] @SallyBercow [who entered Celebrity Big Brother last year]?
"As well as curious as to what whips' office said, most curious as to what Mid Beds Conservative Assn said when she told them. #Dorries.
"The Speaker could be forgiven for a wry smile and a small glass of sherry tonight."
When it was suggested that she was not fit to criticise, having quit her MP role mid-term, Mensch replied: "When I had to leave Parlt to be with my husband, I resigned. One is serious family issue; one is celeb.
"I did everything I could to avoid an early resignation and wish I had been able to. I wasn't."
Watch a promo for I'm a Celebrity below: