RELIGIOUS education in state primary schools discriminates against children whose parents opt out, according to a complaint to be laid today at the Victorian Equal Opportunity and Human Rights Commission.

The complaint by three parents claims the Education Department segregates children on religious grounds and discriminates by forcing children to opt out rather than specifically opting in if they want religious education.

The department also discriminates by denying those who opt out a proper secular alternative, the complaint says.

According to Holding Redlich partner Andrea Tsalamandris, who will lodge the complaint, religious instruction is clearly permitted, ''but we object to the way it is taught''.

She said she had heard stories of prep children having to sit unsupervised in the corridor during religion classes, and of children being made to sit in computer rooms but not allowed to turn computers on.