With growing concern from parents and education experts about the effects of poor quality school meals, Richard has demanded urgent action to bring West Berkshire schools up to speed with other parts of the country.

He said: "There is a clear link between poor quality food and bad behaviour in class, and with more spent on prison food than on West Berkshire school meals, we must take urgent action to restore discipline."

He added: "Dozens of councils across the country are taking steps to improve school diets, but once again, Liberal Democrats have let us down in West Berkshire."

Evidence shows that improving food quality can double the uptake, offsetting an increase in costs to schools and taxpayers, while research also proves that children eating unprocessed foods behave better as they are less hyperactive.

Conversely, the Liberal Democrat policy talks of "opportunities to provide healthy choices", and "opportunities to increase the uptake of meals."

Prompted by Mr Benyon’s attack, the council said it already exceeded government standards - which chef Jamie Oliver has claimed are far too low - after hiring Hampshire County Council’s catering corps to raise standards in West Berkshire two years ago.

Council procurement Contracts Manager Sheila Armstrong - a former Liberal Democrat town councillor - said: “Processed foods and those containing 'E' Numbers are almost totally eliminated from our school meals and we are continually striving to reduce fat, sugar and salt levels. Our menus change every term to reflect the seasons and we already offer freshly prepared foods daily and are already including some organic foods".

It said it had “significantly” cut fat, sugar and salt, and said that desserts are “always” healthy.

Lib Dem councillor for schools Mollie Lock claimed local schools are setting the standard, and are eating more healthily, even though only 43p is spent on ingredients for a local school meal, against 60p for prisoners.