The former Liberty X singer had to call the fire brigade to rescue six-month-old Faith from her BMW in what she described on Twitter as "the worst hour of my life".
"I locked Faith, my keys & my phone in the car. Somehow the car locked when I shut the door," she explained. "Me & Faith owe you.#britishfiremenrule."
However, Heaton was later bombarded with messages from Twitter users condemning her for the incident. One asked why she didn't "just smash the car window", to which the Celebrity Big Brother star replied: "FYI the fire brigade told me not to in case it hit faith as its (sic) a small car! #p**soff."
Another said they were angry at her for "standing around tweeting" while Faith was locked in the car.
"I tweeted that all after you idiot," she claimed. "My phone was in the car with the baby.. Not one tweet left my phone till after men left."
Heaton did receive support from celebrity friend and fellow mother Nicola T, who wrote to her: "These people clearly arn't (sic) parents. Grrrrr makes me want to swear at them!"
"U should have seen the abuse I got for locking faith In the car!" she responded.
Faith is Heaton's first child with second husband Hugh Hanley, who she married in July 2010.