Families who don't believe in God are being failed by Scotland's education system, it was claimed yesterday.

The Humanist Society of Scotland (HSS) warned that both lessons and events such as assemblies in non-denominational schools were largely directed at those who had a Christian faith.

This Saturday, the society will launch an education campaign, founded on the UN Convention on the Rights of the Child, which calls for the humanist view to be more widely recognised.

The HSS will publish new curriculum material for religious and moral education lessons as well as advice to schools and parents about balancing Christian assemblies and visits from ministers with secular alternatives.

Bob McKay, education officer with the HSS, said: "The convention affirms the right of all children to an education that respects both their own cultural values and those of others.

"In Scotland, all parents have the right to raise their children in the religion of their choice, and send them to school in the expectation that their faith will be respected - which is as it should be.

"But no provision of any kind is made for the one in three Scots who have no religious belief. At present, all they can do is ask that their children be withdrawn or excluded from religious activities, which is quite simply inadequate and unfair."

Mr McKay said the HSS wanted equal respect for convictions of humanists and a recognition of the legitimacy of their ethical stance.

Novelist Christopher Brookmyre yesterday lent his support to the campaign, but courted controversy by referring to the Holy Trinity.

"Children necessarily must invest the sincerest trust in what their teachers tell them. Thus the same institution that tells them one plus one equals two should not then be telling them that three persons add up to one God," he said.

Michael McGrath, director of the Scottish Catholic Education Service, said: "Children in all schools in Scotland are taught to respect the beliefs, cultures and traditions of all the great world faiths. They also learn to respect all people, whether they subscribe to a religious tradition or not.

"It is unfortunate that some representatives of other - non-religious - stances seek to define their own views by disparaging the religious beliefs of others, such as the Mystery of the Trinity. It is also insulting to people of faith to see religion characterised as a form of imprisonment' from which children must be set free. This kind of language hardly helps to build a more tolerant and respectful society."

Morag Mylne, convener of the Church of Scotland's church and society council, added: "There appears to be a blurring between religious and moral education and religious observance. It is not the case that other belief systems that don't hold with the Christian faith are currently ignored."