THE battle over ethics classes in NSW schools has been reignited by a threat from the Reverend Fred Nile to ''torpedo'' the O'Farrell government's contentious public sector wages policy unless it considers removing them.

Ethics classes were introduced into schools as an alternative to Scripture classes after the Greens supported legislation brought by the former Labor government last year.

In contention ... ethics classes. Illustration: Cathy Wilcox

The Coalition voted against it in opposition but Adrian Piccoli, who was then the education spokesman, later upset church groups by declaring it would not repeal the laws in government.

But since the election Mr Nile and his fellow Christian Democratic Party MP, Paul Green, share the balance of power in the upper house and the government relies on their support to pass legislation opposed by Labor and the Greens.