A law that compels schoolchildren to take part in collective acts of "reverence or veneration to a divine being" should be abolished because it impinges on children's and teachers' "freedom of belief", a group of unions, humanists and religious organisations argue.
In a letter this week to education secretary Michael Gove, the British Humanist Association claims that "the vast majority" of non-faith schools flout their obligation to hold a daily act of "broadly Christian" worship because of timetable and space restrictions.
The law also forces children to take part in worship regardless of what they believe, the letter says.
A get-out clause in the current legislation allows parents to withdraw their children from worship if they disagree with it, but the campaigners say this forces pupils to miss other aspects of assemblies and isolates them from their classmates.
The association claims the clause has remained in law since the 1944 Education Act because of pressure from religious lobby groups and bishops in the House of Lords.
It said it hopes the Coalition Government will respond favourably to its request, given its policy of removing unnecessary bureaucracy.
The letter says the forthcoming education bill provides "the perfect opportunity" to abolish the law.
Ofsted is already thought to act leniently over the issue.
Brian Lightman, general secretary of the Association of School and College Leaders, a signatory of the letter, said heads should be allowed to make decisions about assemblies and any possible religious content.
He said: "It's been an area of anomalous legislation for some time; the way it is worded is restrictive in the way schools can approach school assemblies, and in many respects it is unworkable."
He said many schools simply did not have the time to schedule daily worship and an alternative "thought for the day" hosted in children's classes depended on the co-operation of class teachers with a range of different beliefs.
"Many schools aren't doing it and theoretically they are breaking the law," he said.
While continuing to stress the importance of assemblies, Mr Lightman questioned whether religion was something you could "coerce people into" and called for reform of the law.
Mr Lightman was joined by representatives of the Christian, Jewish and Muslim communities, including Neville Kenyon, president of the General Assembly of Unitarian and Free Christian Churches; Tehmina Kazi, director of British Muslims for Secular Democracy; and Rabbi Jonathan Romain, chair of the Accord Coalition and minister of the Maidenhead Synagogue.
James Gray, educational campaigner for the association, added that many schools were ignoring the law, while others with Christian headteachers embraced daily worship.
"It is a gross infringement of children and teachers' freedom of belief under the Human Rights Act," he added, saying that the law encourages a "pretence of worship" in schools.
A spokesman for the Church of England, however, said it would be wrong to abolish collective worship.
He said: "To get rid of the act of worship is to deny children the opportunity to experience something they wouldn't experience elsewhere in their lives."