In a week of high sectarian tension, Michael Ancram, the education minister, has introduced tough conditions for the approval of any new integrated schools.
However, he wants to make it easier for existing Protestant and Catholic schools to switch to integrated status and is proposing that only 1 per cent of pupils need be from the minority community.
Integrated schools are roughly equivalent to grant-maintained schools in England and Wales though their intake is supposed to cut across Ulster's religious divide.
The clampdown reflects the minister's worry about rising costs. There are now eight GM secondary and 15 GM primary schools, with running costs of Pounds 7.5 million, and more are opening in September.
The Department for Education and Employment confirmed that the minister had agreed that primary schools will need 25 Year 1 pupils to be approved, compared with 15 at present, and should have a long-term enrolment of 150-175. More than 500 primaries - half the total in Northern Ireland - have fewer than 150 children enrolled.
In the case of secondary schools, the minister has said he will not approve any more GM integrated schools unless they have at least 100 first-formers and a long-term enrolment of 500. About 100 existing secondary schools fall below this figure.
In a new consultation document, Mr Ancram suggests that existing Catholic or Protestant schools should be entitled to integrated status even if only 1 per cent of the total roll or 5 per cent of the annual intake of pupils are from the minority community. This would be a cheaper option for the Government, but the schools would be integrated in name only.
Supporters of integration fear that the new policy is already in operation. Early this year, Mr Ancram allowed the 67-pupil Hilden primary school to become formally integrated even though it has only a tiny number of Catholics.
But he has rejected for the second time an application from the new Oakwood primary three miles away in Derriaghy, even though it has already recruited the religiously- balanced 25 Year 1 pupils needed under the new tougher rules.
John McReynolds, chair of the recently approved North Coast College in Coleraine, which has 82 prospective first-formers, said the requirement for 100 would make it very hard for anyone starting up.
"It is difficult enough to get 60 pupils because parents have to sign up to a hope or a vision - we have no school building to show them and no teachers to talk to," he said. "The higher figure of 100 has been chosen to make it almost impossible to open integrated schools."