According to The Sun, the actress will reprise her role as the chain-smoking English journalist, but producers have promised her they won’t make her pile on the pounds to achieve her character’s rounder frame.
A source told the newspaper: 'Renee had no reservations about saying yes once she found out she wouldn't have to get fat. She hated having to do that in the last two films.'
The movie will start with Bridget stepping off the scales having reached her ideal weight in an attempt to skirt around the issue.
Meanwhile, Oscar winner Colin Firth is expected to return as her boyfriend Mark Darcy.
The source added: 'Colin is really keen on a third film. He's getting very excited about the idea of marriage and kids in the script, now all the characters are older.'