Atheists have hit out at an American civil rights advocacy organisation who published a list of “anti-Muslim extremist” authors.

The Southern Poverty Law Center (SPLC), specialising in civil rights and public interest litigation, published the report earlier this month which included Christian conservatives and two high-profile campaigners credited for their work in the Muslim community.

Critics called the SPLC’s decision “dangerous” and “disgraceful”, and a petition has been launched for the organisation to remove certain members of the list.

"By including liberal reformists and human rights activists in its list of 'anti-Muslim' extremists, the SPLC has effectively chosen to silence and ignore many very important voices from whole groups of marginalized people,” explains the petition.

“In doing so, it is inadvertently accepting the most hardline and fundamentalist interpretations of Islam which chooses to remain divorced from liberal and humanitarian values.”

The change.org movement specifically calls for the removal of Ayaan Hirsi Ali and Maajid Nawaz from the list.

Ms Ali, a Somali-born human rights activist and former Dutch MP, is an an ex-Muslim atheist who has publicly criticised fundamentalist Islamic practices such as female genital mutilation - of which she was a victim.

Mr Nawaz is a practicing Muslim and former recruiter for Islamist group Hizbut Tahrir. He has since launched the Quilliam Foundation, a think tank based in Britain which focuses on issues of anti-extremism, deradicalisation, and counter terrorism.

Heidi Beirich, SPLC’s intelligence project director, said her concern with figures such as Mr Nawaz was the way they "misrepresent" America's Muslim community.

"Our concern specifically with Mr Nawaz is he has spread conspiracy theories about Muslims infiltrating universities and law enforcement, and that kind of conspiracy- mongering to us is not sane discussion on Muslim America," she told The Independent.

"If we're going to talk about Muslims, we want to stay away from that kind of rhetoric, it's a false representation of a community so we are using our free speech to expose that. He can call himself a Muslim reformer but his communications about the community have been absurd - just because he's a Muslim, that doesn't exempt him."

However Mr Nawaz claimed the "regressive left" had issued a "fatwa" against him as a "Muslim reformer".

"I have survived violent neo-Nazi racism and served as a former War on Terror political prisoner in Egypt, witnessing torture," he told the Daily Beast.

"Yet, in a trip that takes us through the looking glass, the largely white American non-Muslim 'progressive' leadership at the pro-civil liberties group Southern Poverty Law Center has just published a 'journalist's field list' naming me as an 'anti-Muslim' extremist."

Mr Nawaz also claimed he was the target of muslim fundamentalists who wanted him dead for his liberal views.

"Meanwhile, from the comforts of sweet Alabama comes this edict that liberal Muslims working to throw open a conversation around reforming Islam today are somehow to be deemed 'anti-Muslim extremists,'" he said.

Other critics suggested the SPLC’s decision discredited them as a serious organisation.

"If criticizing religious beliefs makes them extremists, then it won't be long before other vocal atheists end up on that list too. And make no mistake, that's what Nawaz and Hirsi Ali are doing. That's all they're doing. They're not anti-Muslim; they work with moderate Muslims. They're critical of the worst aspects of Islam," Hemant Mehta of The Friendly Atheist blog said.

However, both campaigners have also been criticised in recent years with Ms Ali being branded a "veiled bigot" after she declared "Islam is not a religion of peace".

The SPLC said the list was published to expose a "network of anti-Muslim extremists and their enablers" creating "propaganda" that served to fuel hatred in the US.

It said a coalition of four research groups SPLC, Media Matters for America, the Center for New Community and ReThink Media, came together to write the manual in the hope that journalists will "use it as a guide to effectively counter these extremists and their damaging misinformation."

"A shocking number of these extremists are seen regularly on television news programs and quoted in the pages of our leading newspapers. There, they routinely espouse a wide range of utter falsehoods, all designed to make Muslims appear as bloodthirsty terrorists or people intent on undermining American constitutional freedoms. More often than not, these claims go uncontested," the report read.