Why Jamie's knives are out for Sarah Palin

The froot-loop is a breakfast cereal full of sugar and containing a bewildering selection of processed grains made attractive to children with the addition of salt, colouring, and fruit flavours. In the world of Jamie Oliver, it's also a term of abuse which can be accurately applied to Sarah Palin.

Britain's fiercest crusader for healthy eating is at the centre of one of the many fierce disputes which now define America's fractured political landscape, after using an appearance in Miami to criticise the former Governor of Alaska's attempts to disrupt a White House campaign against childhood obesity.

Ms Palin is among a selection of big-hitters from the Tea Party movement who have been highly critical of the "Let's Move!" initiative spearheaded by Michelle Obama, which aims to improve the nation's calorie-laden diet.

During a Q&A session at a food festival on Saturday, Mr Oliver was asked what he thought about Palin's stance. He took a deep breath before declaring: "clearly, on this issue, [she] is a fruit loop".

The US is in a "really dark moment" on the issue of children's health said Oliver, who has been filming a series of his Food Revolution TV show in Los Angeles. "The health situation isn't allowing Americans to be Americans," he said, adding that healthy eating was "a civil rights issue".

Cue howls of outrage from supporters of Palin, who resent all criticism of their beloved "Mama Grizzly" – but are never more exercised than when her credibility and patriotism is attacked by an interfering foreigner.

Oliver's comments gain potency since they play into a wider PR battle, which is pitting Mrs Obama and health officials against the forces of conservatism.

Every modern First Lady has spearheaded a social cause: Nancy Reagan ran the "just say no" campaign against drugs, Barbara and Laura Bush attempted to reduce childhood illiteracy, and Lady Bird Johnson planted flowers.

But while their efforts are traditionally applauded, Mrs Obama's effort to make America's children eat their vegetables has prompted a furious backlash from Republicans.

Commentators such as Glenn Beck ("Get away from my French fries, Mrs Obama!") and Rush Limbaugh ("If we are supposed to eat roots, berries and tree bark, show us how!") have fiercely criticised "Let's Move!".

Palin has claimed the First Lady "is telling us she cannot trust parents to make decisions for their own children, for their own families, in what we should eat."