The supermodel marked the start of British Sandwich Week for Hovis by launching the campaign, which celebrates the 250th anniversary of the Sandwiches.
Kidd, whose grandmother was married to the 9th Earl of Sandwich's second son, said: "Sandwiches are one of life's little pleasures and everyone has their own preferences and opinions on how to prepare the ultimate lunchtime treat.
"My family connections to the renowned Sandwich clan meant I jumped at the chance to team up with Hovis to help celebrate the 250th anniversary of the sandwich, which originated during one of the Earl of Sandwich's card games in 1762, and launch a search for the 'Ultimate British Sandwich'."
Jodie Kidd is fronting a search for the Ultimate British Sandwich to celebrate the launch of the new Hovis British Farmers Loaf. Go to The Ultimate British Sandwich website to submit a sandwich today
She added: "My favourite sandwich is an English twist on a continental classic. I love to use ingredients that are sourced from close to home, and living in West Sussex means I am spoilt for choice when it comes to independent farms and regional produce markets.
"My favourite combination is a very ripe Sussex brie, a flavoursome local ham, slices of tomato and some spicy rocket.
"It's a little naughty but tastes divine, especially when served on two slices of warm Farmers Loaf, which melts the cheese further and turns the whole thing into a gooey, yummy feast!"
Entrants can submit their best British sandwich ingredients online for two weeks from today.