Mental health trusts have been accused of 'running scared' from the advent of primary care trusts by building huge organisations which are 'in danger of becoming dinosaurs'.

The national trend to merge mental health services into large specialist trusts has been driven by 'a total lack of clarity' surrounding government policy, according to experts in the field.

Mergers in London this year have created four specialist mental health trusts. Plans for a single trust for Barking and Havering, Redbridge and Waltham Forest will go out to public consultation in October. And East London and the City health authority has come under fire from local community health councils for delaying public consultation on plans for a mental health trust.

London regional office said the mergers were driven by the need to 'conform with government policy supporting single mental health trusts' as set out in The New NHS white paper.

Elsewhere, trusts planning similar changes said their work 'anticipated' the findings of the delayed national service framework on mental health, originally due out in April. They also said mergers would provide mental health with 'a prominent voice' in local health economies.

Mental health services from four trusts formed Avon and Western Wiltshire Mental Health Care trust in April. The trust is now hoping to bring in specialist services from two further trusts.

Chief executive Roger Pedley said it was 'legitimate' to question whether such a trust would have difficulty covering a widely dispersed 1.8 million population. But he insisted that primary care groups should be seen as 'an opportunity, rather than a threat. It is important that there is a prominent voice for mental health alongside PCGs and PCTs,' he said.

Dr Matt Muijen, director of the Sainsbury Centre for Mental Health, said the thinking behind 'empire-building' betrayed 'a total lack of clarity about what these mergers are for'.

'There was one line in the white paper on specialist mental health trusts - beyond that it's unclear where these motives stem from.'

He expressed 'grave concerns about large mental health trusts becoming dinosaurs which will be out of touch from communities they serve'.

'I would find it far more exciting to have far more local services working around PCTs,' he added.

National Schizophrenia Fellowship director Cliff Prior described the growth of the 'supertrusts' as 'a perfectly sensible business strategy'. But he said it was 'obvious' that organisations looking to create large trusts were attempting to 'protect themselves' for fear that mental health services might be sidelined by PCTs.

He called for 'more clarity' about PCTs - 'the wildcard as far as planning ahead in mental health services is concerned' - to ensure structural change was user-led.