But Police Minister Troy Grant argued the changes have the support of NSW Police and are "justified, balanced, improve community safety and enhance our robust firearms regime in NSW".

A bill containing the changes was introduced to the NSW upper house on Wednesday, shortly after the NSW Coroner released his report on the Lindt Cafe siege committed by gunman Man Haron Monis.

It fulfils the NSW government's agreement at the Council of Australian Governments - under the National Firearms Agreement - to reclassify a version of the controversial Adler lever action shotgun with more than five rounds to Category D.

This means only those with a genuine reason - such as pest control by farmers - may be issued a licence for the weapon when the present import ban is lifted once all state and territories have legislated.

But beyond the agreement, the bill also increases the number of Category D firearms - which include semi-automatic rifles and pump action shotguns - eligible farmers may own, from one to three.

It is believed that the government feels this recognises the legitimate needs of farmers.

The bill also dumps a rule that firearms dealers must record the address of those who buy ammunition. Only the name would be recorded under the proposed change.

It is understood the government believes this will ensure registers do not provide a "shopping list" of guns for criminals if stolen.

Other changes include removing the requirement for gun owners to attend court and face a fine and/or a jail sentence for breaches of storage requirements. Instead, police will be able to issue a penalty notice.

As well, police will no longer be required to seize improperly stored firearms and ammunition if they are "satisfied that the failure has been rectified or will be rectified without delay".

Greens MLC David Shoebridge said the relaxation of the number of Category D weapons was particularly concerning in light of the Port Arthur massacre.

He argued ammunition tracking "gives police real-time information that can be crucial for investigating gun crime" and said it was "extraordinary" to relax ammunition controls amid a heightened terror alert.

Safe storage "is essential in Australia's success in reducing firearms deaths, especially suicides," he said.

The chair of Gun Control Australia, Samantha Lee, said it was "devastating that [the National Firearms Agreement] is being used by the government as a political football to win gun votes".

Shooters and Fishers Party MLC Robert Borsak opposed the reclassification of lever action shotguns, but agreed that recording of addresses of people buying ammunition "only gives criminals a shopping list of where legally owned firearms are held".

He said storage control changes were "a smarter way of handling compliance amongst licensed, law-abiding firearms owners".