Police have assured NSW political leaders they are keeping tabs on a small hard corps of white supremacists known to be spreading their gospels of racism, intolerance and hate.

The declaration follows the massacre by Grafton-raised Brenton Tarrant, who remains the only person charged with murder over the Christchurch mosques mass shootings that has claimed the lives of 50 people.

The 28-year-old posted a 74-page “manifesto” online before the attack, and a 17-minute video was also uploaded of him arming himself and entering a mosque where he started shooting.

He also emailed his rambling, hate-filled manifesto to NZ Prime Minister Jacinda Ardern minutes before opening fire

Questions have been raised as to why he did not appear on a watchlist of New Zealand or Australian security agencies.

NSW Opposition Leader Michael Daley said the police minister and police commissioner had told him in briefings on Saturday there are a small number of white supremacists and extremists in the state.

“The numbers are not growing to a degree that would alarm them but they are keeping a very vigilant watch on them,” he told Sky News on Sunday.

“Extremism in all its forms is a one-way street and we have to stamp it out.

“We cannot tolerate violence like this, it doesn’t matter whether they’re white supremacists or other sorts of extremists, we have to reject extremism outright.”

-with AAP