THE state government's plans to introduce ethics classes into primary schools are in disarray after the Coalition announced it would not support them as an alternative to scripture if it wins power next year.

''While the NSW Liberals and Nationals understand the importance of ethics we do not believe it should be positioned as an alternative to special religious education,'' the opposition education spokesman, Adrian Piccoli, said.

''We don't think that students should have to choose between special religious education … and ethics classes.''

On Monday, state cabinet approved a change to the wording of the Department of Education policy which forbids ethics classes being run at the same time as scripture classes.

Under the government's plan, the St James Ethics Centre, which ran a successful trial of the classes in NSW primary schools this year, would provide course material and volunteer teachers for all children from kindergarten to year 6. The program would be funded by donations.