Changes to firearms laws proposed by the NSW government have been savaged by opponents who claim they represent a step backwards for gun control in Australia.

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.