The chief scientist in New South Wales says there should be no CSG fracking in Sydney’s water catchment area until all the risks are known.

The NSW government’s moratorium on coal seam gas activity in the catchment area had been waiting on the release of the Chief Scientist's report.

It has now been handed down, but far from welcoming the resource extraction method, Chief Scientist Professor Mary O'Kane has called for fracking chemicals to be severely controlled or even banned.

She says fracking companies produce water containing high levels of salinity and other harmful chemicals, and must be held to account.

“We've also suggested that in water quality that extra precautions be taken and that produced water - if any CSG activity were to take place - should be treated specially and not just put into the general catchment water,” she said.

Jess Moore from Stop CSG Illawarra says fracking should be banned as there is no safe way to do it.

‘There's lots of questions that actually brings up, things like the cost of constructing treatment plants on site, the environmental implications of constructing treatment plants in our drinking water catchment but also what that's not seriously exploring is the risks of leaks regardless of whether or not that treatment plant is on site,” she told the ABC.

The State Opposition has not spoken on the risks of fracking, but has come out against a somewhat related plan to merge the catchment authority with the State Water Corporation.

NSW Labor's environment spokesperson Luke Foley said the combined body would be less focused and therefore less effective.