Gun control advocates have called for tighter regulation of firearms on the eve of the 20th anniversary of the Port Arthur massacre, saying that landmark gun control measures passed in its wake have since been eroded.

"We don't want laws regressing but that is what I see in NSW and that is why my sister was able to access a firearm," said Michelle Fernando at NSW Parliament on Wednesday.

Ms Fernando's father, Vincent, was shot dead six years ago after his daughter - Ms Fernando's sister - walked out of a pistol club with a semi-automatic pistol and ammunition. She was able to begin shooting despite suffering from a mental illness and paranoid delusions.

A 2008 amendment to the firearms act, passed by the Labor government and Shooters and Fishers Party, allowed people to enter a gun club and begin shooting without a licence and the previous 28-day background check. Ms Fernando believes the watering down of NSW laws led to her father's death.

Ms Fernando and other advocates of tighter regulation of firearms gathered on the eve of the anniversary of the massacre to decry what they say is an erosion in the Howard government reforms that followed that mass shooting of 35 people.

"There's now 3.2 million guns in Australia," said Sam Lee, the head of Gun Control Australia. "Each [Australian] state has eroded its gun laws; chiselled away safeguards".

There are about 850,000 firearms registered in NSW, according to documents released by the police under freedom-of-information laws. That represents growth of about 10 per cent in five years.

The number of guns in private hands nationally now exceeds the amount held before the 1996 massacre, according to a Sydney University study.

Among the reforms called for by gun control advocates are a permanent ban on the A110 lever shotgun, a rapid-fire shotgun that, advocates say, mimics the action of semi-automatic rifles banned in 1996.

The weapon, which can fire up to eight shots in as many seconds, has been temporarily banned from importation to Australia until August. About 7000 of the guns have been pre-ordered and will be delivered after that date unless the ban is extended.

Gun control advocates also want semi-automatic handguns banned.

"They are lethal, easily concealed and the weapon of choice for the criminal classes," said Greens MLC David Shoebridge.

But these claims were disputed by Robert Borsak MLC, a member of the Shooters and Fishers party, which has often held the balance of power in the NSW upper house.

"NSW gun laws have not been loosened," Mr Borsak said. "There's calls for this and calls for that but these are people seeking to further restrict law-abiding firearms ownership for no good reason.

"There's no example I am aware of where a legal pistol has been used in a crime."

Mr Borsak said everyone using a shooting range for the first time without a licence is supervised one-on-one by an instructor.

Gun Control Australia has also criticised other more recent changes to NSW law to expand shooting, including allowing shooting in National Parks and a recent deal between the government and the Shooters and Fishers Party that allows recreational and sporting shooters to apply for "silencers" or suppressors on their weapons.

(Mr Borsak said despite a change to application forms, permits for silencers are not being issued by police).

Four areas for tighter gun control, as called for by Mr Shoebridge.

1. A permanent ban on the Adler A110 repeat-action shotgun
2. Reinstatement of police and mental health checks before firing ranges are used.
3. A strengthening of the requirement to prove to authorities they had a reason for owning each of their firearms. ("We've seen that requirement become a tick-a-box, with gun owners recycling that one reason indefinitely")
4. A ban on semi-automatic handguns