Families in the relatively affluent north-west of the city claim they are being forced into neighbouring authorities or the independent sector because their needs are not being met locally.

Although a quarter of places in Bristol schools are empty, the four secondaries which serve the area are virtually full and the grammar school is heavily oversubscribed.

The group, Parents’ Action for Secondary Education, surveyed the parents of more than 2,300 children in five primary schools.

It found that 95 per cent of respondents would opt to remain with Bristol LEA if a new school was built. Almost 700 prospective pupils were identified.

Bristol is currently losing almost pound;11.5 million in funding for pupils who are educated outside its boundaries.

Plans for a feasibility study - costing about pound;60,000 - will be discussed by councillors next month. Last week, councillors angered parents by refusing to discuss the issue at a meeting of the education committee.

Jan Elliott, one of the campaign leaders, said: “The Labour group seems to find it hard to support what it perceives to be middle- class parents and their privileged children.

“We have been treated shabbily and with contempt. We will now have to go back to our MP and see how we can move things on.”