Police have confirmed that a Perth-based Islamic preacher will not be prosecuted for describing Jews and Christians as "filthy rapists", sparking calls for an urgent review of WA's race hate laws.

Religious and ethnic community leaders said yesterday they were dismayed by the decision not to charge Thornlie man Junaid Thorne after The West Australian exposed his anti-Western preachings and support for the jihadist-group Islamic State last month.

Police reviewed the comments but it is understood they have legal advice that there is little or no likelihood of a successful prosecution.

WA's chief Rabbi David Freilich said he had felt "assaulted" by Mr Thorne's remarks that were contained in a series of videos, which can still be viewed on the internet.

"I find (the comments) absolutely offensive and I think for them to go unpunished is just opening the way for more people to come out with hurtful statements," he said.

Under the State's race hate laws, offenders face up to 14 years jail for conduct intended to incite racial animosity or racist harassment, but there have been only a handful of successful prosecutions since their introduction in 2005.

Australians For Racial Equality president Suresh Rajan said the laws were unnecessarily complicated and did little to discourage those with extreme views on all sides of the political and religious spectrums.

"The legislation is desperately in need of an overhaul," he said.

"You only need to point to the fact that there haven't been many major prosecutions in the past 10 years at a time when racial vilification, particularly against Muslims, has been happening more and more."

Police would not comment on Mr Thorne's case yesterday, but said they would continue to investigate and prosecute individuals when possible.

"The internet has emerged as a means for people to spread inappropriate material and our message to those who do this is simple - you are not anonymous," Assistant Commissioner Nick Anticich said.

It is believed Mr Thorne is currently in Brazil where he has been lecturing to Muslim groups.

On his Facebook page, he recently called for the release of Australian jihadist Musa Cerantonio, who openly supports Islamic State and is accused of encouraging other young Australians to fight in Iraq.