FEARS are growing that tough laws spawned by Australia’s worst mass shooting 20 years ago at Port Arthur, a touchstone in the global gun debate, are in danger of being wound back.

John Howard had been prime minister for just six weeks when Martin Bryant embarked on his wanton slaughter at the former convict settlement, leaving 35 people dead and dozens wounded. Two weeks later, having corralled an agreement out of the states and territories, Mr Howard announced a package of gun reforms including a ban on certain semi-automatic and self-loading rifles and shotguns.

A uniform and stringent licensing system was introduced, including waiting periods, while a national buyback program of banned weapons resulted in more than 700,000 being surrendered. The architect of the 1996 National Firearms Agreement says he remains “wholly against any watering down” of gun laws, and would “encourage a sensible strengthening”.

But since that pivotal agreement in 1996, several states and territories have moved to wind back gun control laws, including Tasmania, which has removed the cooling-off period for buying a second firearm.

More recently it has emerged more than 7000 Adler A110 rapid-fire shotguns have poured into the country in six months, alongside revelations some Australians have amassed huge private arsenals of firearms.

One gun owner, in Cardiff near Newcastle in NSW, had 322 registered firearms. More than 100 postcodes in NSW are linked to more than 2400 guns.

The gun debate is polarising.

Liberal Democratic senator David Leyonhjelm says gun control laws have already gone too far.

“There is an anti-gun push in the Attorney-General’s Department (AGD), and it is literally within the Attorney-General’s Department, and it’s being encouraged by the gun-control lobby to argue for increasing restrictions,” Senator Leyonhjelm told AAP last month.

“There have been documents provided out of the firearms and policy working group which shows the ... firearms group in the AGD have had an agenda of incrementally increasing restrictions on firearms.” And with the introduction and publicity around a controversial Adler A110 - a lever-action shotgun described by gun dealers as a game changer - a new front in the debate has also opened.

“They had their sights on lever-action shotguns, pump-action rifles, magazine sizes,” Senator Leyonhjelm said.

“The reality is the risk has not changed for 20 years, the types of firearms have not changed for 20 years.” The Adler, according to documents released by the Attorney-General’s Department last year under freedom of information rules, has the capacity “to engage targets quickly with a large ... number of 12G shotgun cartridges” is at the forefront of the debate.

Plans to import a seven-shot version of the weapon were halted last July when it was banned by former prime minister Tony Abbott for six months, later extended until August 7 this year, while a review of the National Firearms Agreement took place.

That review is considering whether to place further restrictions on the Adler and other lever-action shotguns.

Mr Howard has rejected arguments from the gun lobby that the Adler should not face further restrictions.

“The Adler lever-action rifle is being argued to be not within the ban and it’s really a weapon that doesn’t have the lethal capacity of automatic and semi-automatics,” he said.

“I’m pretty dubious about that.” It has also emerged that gun dealers are already sidestepping the ban on the seven-shot Adler by using a legal loophole that allows them to modify the weapon and boost its magazine capacity. Mr Howard said he remained sceptical about any changes in gun laws in Australia.

“I’ll naturally wait and see what the inquiry recommends but anything that to me looks as though it waters down the laws that are in place now I won’t support and I will argue that the government shouldn’t support because the experience with these things is when you’ve had a ban in for a long period of time and it’s worked.

“This ban has been so successful, and is so widely respected around the world, that I would not want any government in Australia to do anything that would weaken it.”