Media playback is unsupported on your device Media caption Thornberry: 'They are overweight and that is because of poor eating'

Poor children are overweight, and Labour's plans to extend free school meals to all primary pupils in England will help tackle the issue, the shadow foreign secretary has said.

Emily Thornberry told the BBC that if pupils were given lunch they were "being taught about healthy eating".

Labour says its proposals would be funded by VAT on private school fees.

The authors of a study cited by the party said no link was found between school meals and children's weight.

All children at state schools in England already receive free meals for the first three years of primary school, under a scheme introduced by the coalition government.

After this, parents on low incomes or benefits can apply for their child to continue receiving free meals.

The proposal to extend free meals to all primary pupils was described by Labour last Thursday as a way of improving the health and achievement of many young children.

Questioned about the proposal on the Andrew Marr Show, Ms Thornberry, who received free school meals at the Guildford secondary modern school she attended, said part of a state school educational experience should be having lunch together.

She said: "Part of that is being taught about healthy eating.

"If you look at poor children now, they are not thin, they are overweight and that is because of poor eating, because of bad eating habits, and part of your education ought to be teaching you about, you know, how you'd grow a carrot."

'Slight improvement'

In its announcement, Labour referred to a 2012 report from the Institute for Fiscal Studies, evaluating free meal pilot projects, which found "increased attainment in disadvantaged areas".

Shadow education secretary Angela Rayner highlighted a study that suggested many working families on low incomes and in multiple jobs did not quality for free school meals.

Image copyright Reuters Image caption Pupils at state primary schools in England currently receive free meals in their first three years

But the co-author of the report, Lorraine Dearden, said it had concluded more research was required.

She said there was a "slight improvement" in pupils' attainment, but "we certainly do not know if this impact will replicated nationwide".

She added: "We found there was no impact on absences so it wasn't through children attending school more, there was no impact on things like BMI, body mass index."

The Independent Schools Council said Labour's "sums do not add up" and would hurt hard-working families.

The system for receiving free school meals in Wales is the same as England.

Scotland has its own scheme, with similar entitlements, while in Northern Ireland parents need to apply for free school meals for children of all ages.