They claim the policy, announced by Nick Clegg at the Lib Dem conference in Glasgow this week, also has sound health and economic advantages.
They point to evidence taken from the two pilot schemes which ran in ran from 2009 to 2011 in Durham and Newham, east London. All primary school children in these areas were given free lunches, and data collected to assess whether, and how, it affected their health and academic performance.
The take-up of meals soared from 50 per cent in both areas to 72 per cent for Newham and 85 per cent for Durham. The average midday meal improved significantly: consumption of sandwiches fell by 27 per cent, soft drinks by 16 per cent and crisps by 18 per cent, while consumption of vegetables rose by 23 per cent. Long term the benefits to health and subsequent cost savings could be significant.
Academic results were impressive too. Children in the pilot areas quickly moved ahead of their peers elsewhere, by almost a term.
Nick Clegg, who announced the plan at the Lib Dem conference in Glasgow, says the policy will benefit 1.5 million children and will be worth more than £400 a year for each child aged five, six or seven.
For a closer look at some of the results, visit the Children's Food Trust: http://www.childrensfoodtrust.org.uk/Root/schools/advice/schools/schools-and-las