The acting chief executive of Ashworth Special Hospital is to leave following an unexpected invitation to head the new North West Regional Mental Health Development Centre.

Peter Clarke took up the Ashworth post six months before last January's Fallon inquiry confirmed allegations that a ward in the personality disorder unit was home to pornography, drug abuse and unsupervised contact between paedophiles and a young girl.

Its report said the hospital's 'negative, defensive and blame-ridden culture' was 'so deeply ingrained that we doubt even the most talented management team could turn it around'.

Since then, Mr Clarke has put an action plan in place to increase security and strengthen links with local mental health services.

He will be replaced by Lezli Boswell, who will be seconded from her post as clinical executive for Mental Health Services of Salford trust, from where Mr Clarke was seconded from the chief executive's post in 1998.

Recruitment for the substantive post is unlikely to happen ahead of the establishment of a wider mental health trust, including Ashworth and MHSS trust, scheduled for April 2001.

In a statement, Mr Clarke said he 'had expected to stay at Ashworth until arrangements for us to become part of a new mental health trust become a reality next year.'

But he said: 'People who know me will understand why this particular role - with its responsibility across the whole range of mental health services within the North West region - is so attractive to me.'