One of Australia's leading experts on Islamic extremism has described Sharia law fundamentalists as a 'danger' to society that conservative Muslims needed to challenge.

Professor Greg Barton, a global Islamic politics expert from Melbourne's Deakin University, said hateful rhetoric from hardline Islamist groups had the potential to radicalise a small number of disaffected young people.

Even if they didn't preach violence, Professor Barton feared they would convince a follower they needed to physically punish or even kill non-Muslims.

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One of Australia's leading experts on Muslim extremism has described fundamentalist Islamic groups as a 'danger' to society (pictured is Salafist sheikh Jamil El-Biza)

'"We will follow through and do what these beliefs require", that's the danger,' Professor Barton told Daily Mail Australia from Indonesia.

Fundamentalists in the suburbs have been telling Muslims to avoid wishing Christians a Merry Christmas and demanding that wives should never refuse a husband's demand for sex.

Salafist Muslim groups advocating a fundamentalist, seventh-century version of Islam, operate in parts of Sydney and Melbourne and are funded by Saudi Arabian interests.

The Ahlus Sunnah Wal Jamaah Association, also known as the ASWJ, is an extreme example.

Professor Greg Barton (pictured), from Deakin University, said hateful rhetoric from hardline Islamist groups had the potential to radicalise a small number of disaffected young people

Jamil El-Biza, a fundamentalist sheikh from Wollongong south of Sydney, last year told his followers via Facebook they should avoid wishing Christians a Merry Christmas to please Allah

Jamil El-Biza, a fundamentalist sheikh from Wollongong south of Sydney, last year told his followers via Facebook they should avoid wishing Christians a Merry Christmas to please Allah.

'I'd rather be resurrected on the day of judgement, with the fact I made a few hundred million unhappy with me because I refuse to say "Merry Christmas", rather than being brought forward before Allah and having to explain to him why I congratulated a Christian who worships Jesus as lord,' he said on Christmas Day, 2017.

Professor Barton said fundamentalist groups needed to be called out for pushing anti-social messages.

'So when you've got a group that's putting hatred or intolerance or misogyny, you've got to call it out and say, "That's not acceptable",' he said.

Nassim Abdi, a fundamentalist Sunni at an Auburn mosque in Sydney's west, said it was a 'major sin' for a wife to refuse a husband's demand for sex

Another ASWJ preacher Nassim Abdi last month told a mosque at Auburn, in Sydney's west, that it was sinful for a wife to refuse sex with her husband.

'If the husband calls the wife to be intimate and there's no legitimate reason for the woman to say no, then she must answer the call of her husband,' he said.

'She must answer the call of her husband and if not she has committed a major sin.'

Professor Barton said Australian authorities needed to ask other theologically conservative Muslims to tell extremists they had crossed a socially-acceptable line.

'Perversely, it actually means working with some of the more conservative groups and making it clear where the boundaries are and say, "Look, we fully respect you having your personal beliefs but when it comes to misogyny, child marriage, when it comes to any kind of teaching that incites hatred of others, that's not acceptable",' he said.

'What you want to do is identify where the line is in terms of behaviour.

'You're living in a society where a lot of people celebrate Christmas, you need to educate the next generation to grow up in that multicultural society and not feel threatened.

'When you feel angry, it's not good for you, it's not good for your community.'

Another Sunni hardliner, Umm Jamaal ud-Din, a niqab-wearing Muslim convert from Christianity, previously known as Mouna Parkin, earlier this year told Muslims to boycott Valentine's Day because it had originated as a Christian festival.

'Roses are red, violets are blue, celebrating Valentine's Day is from what the immoral people do,' the religious instructor from western Sydney said.

Muslim convert Umm Jamaal ud-Din (pictured) earlier this year told Muslims to boycott Valentine's Day because it had originated as a Christian festival

Another Islamist group Hizb ut-Tahrir, a political group pushing for an Islamic caliphate, is so extreme it last year confirmed it supported the death penalty for ex-Muslims.

The Australian government is continuing to resist calls to ban this group, even though it is illegal in a range of Muslim-majority nations including Indonesia, Egypt and Jordan.

Sydney Lindt cafe siege gunman Man Monis was photographed attending Hizb ut-Tahrir events before he killed manager Tori Johnson in December 2014 at the end of a 16-hour siege.

Less than a year later, 15-year-old schoolboy Farhad Jabar gunned down accountant Curtis Cheng outside the New South Wales police headquarters in Parramatta, after reportedly visiting a Muslim bookshop in western Sydney selling Sharia law books that advocated death for homosexuals and stoning for adultery.

Sydney Lindt cafe siege gunman Man Monis (pictured) was photographed attending Hizb ut-Tahrir events before he killed manager Tori Johnson in December 2014 at the end of a 16-hour siege

Schoolboy Farhad Jabar, 15, gunned down accountant Curtis Cheng outside the New South Wales police headquarters in Parramatta, after reportedly visiting a Muslim bookshop

Professor Barton said Saudi-funded Islamic Salafist groups had been sprouting up in Australia since the late 1970s and were a challenge to contain.

'In most societies, it's going to be a hopeless battle trying to take on all religious fundamentalists of whatever form including the Salafists,' he said.

Last year, One Nation leader Pauline Hanson wore a burqa into the Senate to make a point about how fundamentalist Islam was incompatible with Australian society.

Professor Barton said stunts like that only helped fundamentalist portray themselves to their followers as being under attack from the West.

'The message of the fundamentalists is that the West hates Islam, that the Australian government, the Australian people are against Muslims so when Pauline Hanson turns up in the Senate in a burqa, it just makes it that much easier for the local preacher who's pushing an intolerant message to turn around and say, "I told you, guys",' he said.