Northey and Spreadbury failed to impress host and judge Elle Macpherson, who broke the news on the Sky Living show this evening.
All 13 girls took part in a catwalk challenge with former US supermodel Janice Dickinson and a Lipton's photoshoot where they had to bring to life different flavours of the popular tea brand.
Spreadbury was heavily criticised by the judges, who were joined by special guest Sophie Ellis Bextor as they assessed the girls pictures.
"Kimberleigh was really clumsy on the shoot and took it a little bit too far. A bit pantomime," said Charley Speed.
Julien Macdonald added: "She looks like a pantomime horse. She just looks huge."
A tearful Spreadbury said afterwards: "I tried my hardest, but it wasn't enough. I didn't want it to happen, but it did."
Northey commented: "Maybe they didn't see the diversity in my poses. I can always go into the agencies in London, Paris, Milan, New York. There's plenty of work out there."
Britain & Ireland's Next Top Model continues next Monday at 9pm on Sky Living. The challenges will include a dramatic makeover and the nude shoot task.
Kimberleigh on the left
Joanne on the right