After 10 minutes, an allen key dropped into the crate and the first to escape by undoing all three bolts would win dinner for their camp.
Wearing goggles, shirts and shorts, the pair nervously stepped into their crates.
After seconds, Flanagan shouted "I'm A Celebrity...Get Me Out Of Here!" and she was helped out of the crate.
Dorries (55) lasted just four minutes and said: "That was possibly the most horrific thing I've ever done in my life.
"It stopped for me when something started biting my leg.
Flanagan sobbed and said: "I'm really struggling.
"I've even been thinking of going because I just don't know if I can hack it."
While Dorries was still shaking bugs off her, Flanagan complained she had a twig in her hair.
Dorries and Flanagan will go head-to-head again in tonight's challenge after being voted in by the public.