More than a fifth of children with eating disorders seen by the South London And Maudsley NHS Foundation Trust are waiting too long to begin their treatment.

NHS guidance says patients should begin treatment within four weeks of referral, or within one week for urgent cases.

The latest figures from NHS England show only 79 per cent of children and under 19s referred to the trust began their treatment within those windows in the 12 months to June, putting its performance below the national average.

Across England, 81 per cent of patients began their treatment within the target window over the same 12-month period, and in some parts of the country the number reached almost 100 per cent.

Cases rose from 266 to 282 between July 2016 and June 2017 in the trust, reflecting national trends.

A spokesperson for the trust said as well as an increase in referrals, there were a “range of reasons” behind the delays.

“Over the last year, we have seen an increase in referrals following an initiative to accept self-referrals from parents, young people, schools and online,” they said.

“There are a range of reasons why patients have waited longer than four weeks for treatment, for example being unable to attend appointments or completing treatment in another service before starting the eating disorders programme.”

While it was not meeting targets for 21 per cent of patients, nearly all patients in routine care were seen within five weeks, they said. 

“Our child and adolescent eating disorders service has focused on treating patients in need of urgent treatment within one week and we have achieved 98 per cent, which is well above the national average,” they said. 

“We appreciate that any delay to receiving treatment for eating disorders can be a difficult and often distressing time, especially for children and their families.”