Headteachers' powers to discipline disruptive pupils are being undermined, according to Harpenden MP Peter Lilley.

Conservative MP Mr Lilley has spoken out after national statistics published last month showed the number of permanent exclusions has been cut by more than a third since 1997.

Mr Lilley said: "Disruptive pupils have been kept in class or in school to the detriment of both themselves and other pupils.

"Vulnerable children need special help and local teachers are best placed to make decisions on exclusions."

The Department for Education and Standards is not publishing the latest exclusion figures until July. The most recent local figures for Hertfordshire show a 36 per cent cut in the number of permanent exclusions in Hertfordshire secondary schools between 1997-98 and 1999-2000.

Mr Lilley said:"I would be pleased if these figures reflected an improvement in pupil behaviour, but I fear that the reduction in the number of permanent exclusions is due to headteachers' hands being tied."

In 1998 the Government set a target for permanent exclusions to drop by a third by this year. In order to achieve this local education authorities were instructed to fine schools up to £6,000 per year for excluding a disruptive pupil. The Government has since abandoned these policies.

Mr Lilley said: "These arbitrary targets have served to undermine discipline, weaken headteachers' authority and lower morale in Hertfordshire schools."

A spokesman for Hertfordshire County Council said: "In recent years a pupil retention grant has been made available to help reduce the need to exclude and to reduce levels of truancy. A small part of the grant is linked to individual excluded pupils to aid in their education."

"A number of Hertfordshire schools have used the money as part of a behaviour modification strategy.

"Where there have been reductions in rates of exclusions it has been the due to the school's own inclusion policies."

Hertfordshire County Council executive member for children schools and families Robert Gordon said: "We recognise the effect that unacceptable behaviour of a few children has on the hard working majority and on school staff.

"Greater clarity has been introduced to re-affirm that exclusion must remain the right response to behaviour that undermines the learning opportunities and possibly the safety of others."