Elliot School has been imposing unlawful £50 fines on parents whose children were caught smoking in the playground.

Margaret Peacock, headteacher of the Putney school, is now having to pay back the money after wrongly claiming powers under the 2007 smoking ban.

The school thought it could use the legislation to clamp down on underage smoking, but it turned out only a council officer could impose such fines.

Mrs Peacock sent letters to parents demanding the £50 and and warned them that if they did not pay, the school's governors would face a £2,500 fine.

In the letter, she wrote: “The law, which came into force on 1 July 2007, prohibits smoking on public property.

“Your child was part of a group of girls seen on CCTV who were involved in smoking on the school site and therefore a fixed penalty fine of £50 has been imposed.”

She added: “The governors, as employers and owners of the property, have a duty to enforce this law and have the right to fine any person £50 for breaking the law.”

The incident, which is thought to be the first of its kind, is now under investigation by Wandsworth Council.

Angry parents like Mavis Lydon, a traffic warden whose 14-year-old daughter Marisha Hamilton was caught smoking, said they had been “ripped off”.

She told the Evening Standard: “There are other ways of punishing children, the school was out of order really. Detention or something like that would've been fine. It's the children who have done wrong, why should the parents have to suffer for it?”

Wandsworth Council has ordered the fines be paid back.

A spokesman said: “We were not aware the school had misinterpreted the law in this way.”

Elliot School, in Pullman Gardens, was put into special measures last year after Ofsted decided it was failing its pupils.

Margaret Peacock, headteacher of the successful Chestnut Grove School in Balham, was brought in to manage the school before a new head could be found.

She was unavailable for comment when contacted by the Wandsworth Guardian.