Atheists and Christians are more likely to be sparring these days than seeing eye to eye, but new powers being proposed by the government are making both groups shudder.

They say the Extremist Disruption Orders (EDOs) recently put forward by the Home Secretary Theresa May could see ordinary people cast in the same light as radicals like Boko Haram, a militant group currently tearing up northern Nigeria.

The EDOs have been proposed as a possible measure against Islamic extremism but the Christian Institute said they could result in anyone who criticises same-sex marriage or Sharia law being defined as "extremist".

Christian Institute's Simon Calvert said: "Anyone who expresses an opinion that isn't regarded as totally compliant with the Equality Act could find themselves ranked alongside Anjem Choudary, Islamic State or Boko Haram."

He added: "How many times a day do intellectually lazy political activists accuse their opponents of 'spreading hatred'?

"The left does it, the right does it, liberals do it, conservatives do it, it is routine.

"Hand a judge a file of a thousand Twitter postings accusing this atheist or that evangelical of 'spreading hatred' and they could easily rule that an EDO is needed.

"It's a crazy idea – the Conservatives need to drop this like a hot brick."

Director of the National Secular Society, Keith Porteous Wood told The Telegraph newspaper that he similarly feared secularists who object to Sharia law would be called "racist" or "Islamophobic".

He said the EDOs sounded "draconian" and could result in powers that are "almost unchallengeable and deprive individuals of their liberties".