Teachers and pressure groups are urging the education secretary to scrap a law requiring pupils in England to take part in a daily act of collective religious worship.

The National Secular Society (NSS) has written to Michael Gove arguing that the legislation, dating from the 1944 Education Act, infringes children's human rights and discriminates against pupils of no faith and non-Christians.

The law states that all pupils in primary and secondary schools must participate in a daily act of worship that is "wholly or mainly of a broadly Christian character". Parents can write to a school to withdraw their children, but the NSS said many did not out of fear it could single out their children as different and expose them to bullying.

Headteachers say the law is unworkable because few schools can hold an assembly for all pupils. Paul Kelley, the head of Monkseaton high school, Tyne and Wear, said most schools were ignoring the law. In 2005, Kelley asked the Labour government if the law could be abolished, but said he was told the change "would never get through the House of Lords".

In his letter to Gove, Keith Porteous Wood, executive director of the NSS, writes: "We believe that the mandatory daily acts of mainly Christian worship and in particular, the imposition on children to take part in such acts, represent an ... infringement of rights.

"We recognise that assemblies with an ethical framework have a vital contribution to make to school life. We do, however, object to collective worship in principle, as not being a legitimate activity of a state-funded institution.

"We are confident that you would not wish to perpetuate a law that is routinely disregarded. We hope that, under your leadership, the law will be changed so that it is brought out of disrepute."

The NSS suggests that changes are included in an education bill to be published next year.

The British Humanist Association has also written to Gove on the matter, while the Association of School and College Leaders (ASCL) has backed calls for the law to be dropped. "Many schools aren't doing [the daily act of worship] and theoretically they are breaking the law," Brian Lightman, general secretary of ASCL said.

The Department for Education said the government had no plans to amend the law. "The government believes that the requirement for collective worship in schools encourages pupils to reflect on the concept of belief and the role it plays in the traditions and values of this country," a spokeswoman for the DfE said.

"Schools have the flexibility to design provision that is appropriate to the age and background of their pupils. If the headteacher feels it is inappropriate to have Christian collective worship, the school can apply to have this changed."

The Church of England said daily worship gave pupils an opportunity to develop an understanding of those "with whom they share society". A spokeswoman said: "To deny children the entitlement to take part in worship at school is to deny them a learning experience that is increasingly important in the modern world."