Salty and sugary snacks would be banned under the guidelines

New guidelines require head teachers to draw up healthy lunch box policies on what makes a nutritional packed lunch.

A template policy, linked to the guidelines, bans snacks like crisps and chocolate, and suggests packed lunches are "regularly reviewed".

Head of the ASCL teaching union John Dunford said policing the contents of pupils' lunch boxes was a step too far.

Letter home

Dr Dunford said: "If we have a healthy lunch box policy - it's a pretty short distance between that and Ofsted coming in and saying you are failing in that duty if they spot a packet of crisps in a lunch box.

"If that is the expectation, it goes a step too far."

He added: "There's very little we can do if children bring in a can of fizzy drink and a packet of crisps."

The cross-departmental guidelines, launched on Wednesday, link to a sample policy which urges parents to ensure the pack lunches they provide form part of a balanced diet.

Teaching or catering staff are urged to review packed lunches and reward ones that meet the guidelines with congratulatory stickers or letters home.

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"Parents or pupils who do not adhere to the packed lunch policy will receive a leaflet informing them of the policy.

"If a child regularly brings a packed lunch that does not conform to the policy then the school will contact the parents to discuss this," it says.

The move comes after recent surveys suggested the take-up of school meals had declined since healthy food guidelines were introduced.

A Department for Children, Schools and Families spokesman said: "We are not going to legislate for what's in children's lunchboxes.

"But parents are telling us that they want more advice on what they should be putting in packed lunches. I think it is only right that all schools should have clear advice � as many already do."

She said junk food had already been banned from vending machines and tough new nutritional guidelines ensured children were getting healthy, balanced school meals.

She added: "Now it makes sense for us to make sure - with heads and parents and governors - that children having packed lunches are getting the same opportunity for healthy meals."