An MP's call to ban teachers from telling pupils that gay marriage is "wrong" has been condemned as a "gross infringement of free speech" by campaigners.

Mark Spencer, Conservative MP for Sherwood, said Extremism Disruption Orders (EDOs) should be used against those who teach traditional views on marriage in schools.

EDOs were introduced by the government as part of its measures to crack down on hate speech, amid rising concerns about radicalisation in the UK. Spencer made his comments in an emailed response to a constituent.

"I believe that everybody in society has a right to free speech and to express their views without fear of persecution," the MP said, according to the Telegraph.

"The EDOs will not serve to limit but rather to guarantee it: it is those who seek to stop other people expressing their beliefs who will be targeted."

He continued, however, by highlighting the discussion of gay marriage in schools, and said the belief that same-sex marriage is a sin could constitute "hate speech" in some contexts. While teachers can express their own understanding of marriage, they cannot specifically teach that same-sex marriage is wrong, he added.

He insisted that this does not violate individual liberty because "No citizen is required to accept, condone, support, or promote any political view or ideology as a result of the new legislation."

Campaigners have condemned Spencer's comments.

"This is exactly the kind of thing we've been warning about," Simon Calvert of the Christian Institute told the Telegraph.

"The Government says we've got nothing to worry about from their new extremism laws, but here is one of its own MPs writing to a constituent saying EDOs would stop teachers teaching mainstream Christian beliefs....EDOs will be a gross infringement of free speech and undermine the very British values they claim to protect."

Executive director of the National Secular Society, Keith Porteous Wood, branded EDOs "the largest threat to freedom of expression I have ever seen in Britain."

"The spreading of hatred is far too vague a concept to be the basis of legal sanctions, and would be worryingly open to misuse, particularly by ideological opponents," he added.

Claire Fox, founder and director of the Institute of Ideas think tank, last week accused Cameron's government of "betraying" civil liberties by "dictating what teachers teach in schools".

"Apparently a British value now is a positive acceptance of what the Government has told you it is," she said.