Evidence collected for the report, entitled Evangelism in State Schools, showed it was not just faith schools that had opened their doors to evangelical groups.

• Read: R.E. 'marginalised' in schools

A new study warns that through the marginalisation of religious education, Evangelical Christian groups who are committed to converting young people are being allowed access to children in state schools.

The National Secular Society (NSS), which published the report, has called on the Government to bring in a stricter code of conduct to prevent visiting groups “proselytising” during religious lessons.

According to a report in The Independent, Head teachers’ leaders have warned “a line is crossed” when religious theories such as creationism were taught as if they were science.

Labour leader Ed Miliband has criticised the Church of England legal bar in today's Government statement on equal marriage.

Miliband also pointedly noted that his shadow cabinet were united in favour of gay marriage as well as the "vast majority" of Labour MPs.

"I am pleased that the Government will finally bring forward legislation to allow equal marriage and that we have succeeded in making sure that religious organisations that want to carry out same sex marriages will be able to do so," he said.

"However, it is disappointing that the Government is making same sex marriage illegal in the Church of England.

"The Labour Party has a long and proud history of campaigning to end discrimination against same sex couples and it is Labour votes which will ensure that this measure is passed in the House of Commons."

Political Editor Tom Bradby believes the equal marriage row could be potentially damaging to the Prime Minister at the next general election:

Culture Secretary Maria Miller has promised no church would ever be forced to conduct a gay wedding as she faced a furious backlash from traditionalist Tories over Government plans for same-sex weddings.

Political Editor Tom Bradby reports: