The government is set to retreat from its clampdown on school exclusions.

After complaints that the campaign to cut exclusions was keeping too many disruptive pupils in the classroom, the education secretary is set to write to schools this week with a "clarification" of government policy.

It is expected that this will tell headteachers and school governors that where pupils are violent or threaten the safety of students and staff they can be quickly excluded.

This follows complaints from teachers' unions that the efforts to reduce exclusions had created a growing discipline problem in which schools felt unable to remove anti-social and aggressive pupils.

There had also been a complaint on behalf of school support staff by the public sector union, Unison, claiming that its members were facing an increase in assaults as a result of the shift to fewer exclusions.

However the Department for Education says that despite the forthcoming "simplification" of guidelines, the target for cutting exclusions by a third must still be met by 2002.

A spokesman rejected that there had been any reversal of policy and said that the government would still be keeping a "close eye on schools" and exclusions.

Allowing schools to return to high levels of exclusions would only mean "pushing the problem elsewhere", with excluded pupils being shunted between schools and running the risk of long-term absenteeism and delinquency.

The government's efforts to reduce exclusions were made in response to an upward spiral in pupils being removed from school.

There had been claims that schools were seeking to improve their ranking in exam league tables by excluding large numbers of troublesome and underachieving pupils - leaving these pupils out of the school system for long periods.

Schools were encouraged to consider alternative forms of punishment - and this year saw the first fall in the numbers of pupils being excluded since records began five years ago.

But the apparent relaxation of the exclusions guidelines has been welcomed by teachers' unions.

"This seems to be a good dose of realism where it is badly needed," said Nigel de Gruchy, general secretary of the National Association of Schoolmasters Union of Women Teachers.

"If the government is about to clarify its guidelines on exclusion, this would be very welcome because head teachers have found considerable difficulty in operating them," said John Dunford, general secretary of the Secondary Heads Association.

Describing the move as a "staggering climbdown", the Conservative education spokeswoman Theresa May, said that the government should "abolish targets for exclusions and leave such matters to the discretion of heads in each school".

"We will not allow one disruptive pupil to distract pupils who want to learn from doing so."