Great Ormond Street hospital, which treats 78,000 children a year from all over the country, had some of the worst results in the league tables. It saw only 63 per cent of children at its outpatient clinic within 30 minutes.

Even more alarming was the long wait suffered by many children to receive in-patient treatment.

Three quarters of children needing bladder and kidney treatment had to wait more than three months to be admitted.

Two-thirds of the children needing treatment for ear, nose and throat, eye conditions and oral surgery had to wait more than three months.

Nearly half those needing general surgery, bone or joint treatment had to wait more than three months.

These long delays come on top of the time waiting to see a local hospital consultant before being referred to Great Ormond Street. (The hospital will not normally take any direct referrals from GPs.)

Sir Anthony Tippet, chief executive of the Great Ormond Street Trust, admitted the figures were bad: 'I realise we need to improve our performance.'

One of the main reasons for the long wait was the heavy demand on specialist services available at the hospital, he said.

'There is a good reason for our waiting times. There is a very big demand on our services which are very specialised. These areas are represented by distinguished people in their field.'

Although the consultants would carry out private work as well, he said they worked extremely hard for the NHS: pounds 6m of the hospital's pounds 90m budget had to be raised from private practice, while pounds 10m came from donations and the support of trustees. The hospital intends to tackle the problem by improving the way clinics are organised, avoiding lengthy waiting around while tests are carried out.

It has appointed an extra consultant in urology to deal with that backlog, though Sir Anthony admitted it will not be possible to do that in every speciality.

Some of the capital's other top hospitals have widely varying performance rates.

Only a third of the patients attending the Royal National Orthopaedic Hospital, which specialises in bone and joint treatments and hip replacements, were admitted within three months.

But on a more successful note, the Royal National Throat, Nose and Ear Hospital admitted 73 per cent of its patients in that speciality within three months.

Guys and St Thomas' hospital also did relatively well, with three five star ratings - the top award possible - for the percentage of patients admitted within three months. This was out of eight specialities.

And St Bartholomew's did even better, scoring five stars in four categories for waits less than three months. The Royal London Hospital also scored highly.

But even those which did well in some specialties, such as general surgery or gynaecology, fell down on others.

Orthopaedic patients at the Royal London were in for a much longer wait, with only 46 per cent seen within three months. Guys and St Thomas's also saw only half its orthopaedic patients within three months.

Barts had a similarly long wait for ear nose and throat - only 43 per cent were admitted within three months.

Virginia Bottomley, Secretary of State for Health, said some of the best - and worst- examples were in the North Thames region.

She said the league tables supported the Tomlinson report recommendations that the capital's scattered specialist provision was better centred on a smaller number of units which could be more cost effective. 'It isn't an argument against Tomlinson, it is an argument for rationalising the speciality services in London.'