Lancashire Care NHS Trust is taking longer to see children with eating disorders than will be allowed by targets to be imposed next year.
With the NHS missing the soon-to-be introduced target for waiting times across England, leading mental health charities say patchy provision of services leaves many youngsters waiting too long for access to vital care.
NHS guidance says patients will have to begin treatment within four weeks of referral in 2020-21, or within one week for urgent cases.
But just 76 per cent of children and under 19s referred to Lancashire Care NHS Trust were seen within four weeks between October 2018 and September this year, the latest NHS England statistics show – meaning 52 youngsters waited longer for treatment.
This is far below the 95 per cent target which will be set for all NHS trusts and other healthcare providers by next year.
Waiting times for urgent cases also lag behind the target – of 45 urgent cases processed over the period, only 26 (58 per cent ) were seen within one week.
The target referral window follows extra investment, provided in 2015, aimed at improving eating disorder services across the country.
Nationwide, only 85 per cent of young patients were seen within four weeks for routine cases, and 79 per cent within one week for urgent ones.
Commenting on the figures, mental health charity YoungMinds welcomed the "good news" that more young people are receiving faster treatment for urgent disorders, but cautioned there is "still some way to go" to meet targets.
Tom Quinn, director of external affairs at eating disorder charity Beat, said sufferers face a "postcode lottery" for treatment.
He added: "Whilst waiting times have shortened compared to the same quarter last year, people with eating disorders are still at risk of feeling that they are 'not ill enough' to be seen quickly.
"In addition, waiting times standards help sufferers who have already been referred for treatment but it still takes nearly three years, on average, for someone to realise they have an eating disorder and visit a GP.
"We need more awareness and support for sources of information so that people are encouraged to seek help as soon as they feel unwell."
Overall, more youngsters with eating disorders are now starting treatment in England than a year ago.
In the year ending September, 7,695 patients started treatment – up from 7,134 over the previous 12 months.
Lancashire Care NHS Trustalso saw cases rise during this time, from 218 to 261.