New South Wales Labor has hit back at the Coalition’s campaign to link them to the Shooters, Fishers and Farmers party because of a preference deal they have struck, producing a dossier highlighting the political deals that the Coalition did with the Shooters over the past eight years.

Former prime ministers John Howard and Tony Abbott joined criticism of Labor’s preference deal with the Shooters, saying it will lead to more lax gun laws, following the deadly Christchurch terrorist attacks.

Labor is directing preferences to the Shooters ahead of the Nationals in two marginal regional seats, among others, on its how-to-vote cards – Upper Hunter and Barwon – where Nationals candidates are at serious risk of losing to Shooter candidates in three-cornered contests. The Liberals say the preferences are being directed in 20 seats.

Howard said Labor would “do anything to buy a vote” in an advertisement published on the NSW Liberals’ Facebook page on Sunday night.

The Shooters have argued for a repeal of the 1996 National Gun Control Agreement and, if Labor were to win the state election it would put “enormous pressure” on the party water down the laws, Howard said.

“And that would be at a great cost to community safety. What that preference deal demonstrates, is that Labor will do anything to buy a vote, and it’s a reason not to reward that kind of attitude,” he said.

On Monday Abbott joined the attack, telling 2GB Radio that “any suggestion we should be watering down our gun laws is crackers” and arguing “Michael Daley needs his head read for getting into bed with the Shooters at this time”.

Labor has now produced a dossier of statements by NSW Liberal and National MPs supporting relaxation of gun laws and deals they have struck with the Shooters.

These include the National party leader, John Barilaro in 2017 asking a parliamentary committee to review the law relating to the use of firearms in self defence; the rejection of tighter gun laws proposed by the NSW Police after pressure from the gun lobby, and the 2012 deal with the Shooters to allow amateur culling of feral animals in national parks.

The Shooters regard the government as having dudded them on the promise to allow shooting in national parks, which was trialled but not permanently implemented.

On Sunday the premier, Gladys Berejiklian, called for the opposition leader, Michael Daley, to cut ties with the Shooters, a party she said wanted to put guns in the hands of 10-year-olds.

“It concerns me because it legitimises a party, being the Shooters, who support the reduction or dilution of our gun laws,” Berejiklian told reporters.

Daley was forced to rule out weakening NSW gun laws if he were to become premier while on the hustings in western Sydney, where Labor announced $100m for six ice rehabilitation clinics across the state.

“I will not be a part of parliament that weakens the gun laws in NSW. It will not happen if I am premier,” Daley told reporters.

“There’s a big leap between what’s on a how-to-vote card and legislation.”

Abbott suggested Daley was “not fit to be premier”, accusing him of telling “lies” in an interview in which the opposition leader told Alan Jones he would sack him and the rest of the Sydney Cricket Ground trust if elected.

“I think it would be a disaster for New South Wales if there were to be a change of government.

“We have a massive and overdue infrastructure program – half of it would be cancelled if Labor were to win.”

The latest polls suggest the Berejiklian government is at risk of losing the state election, with new seat polling showing swings of up to 6% against it.

The latest YouGov Galaxy poll shows the seats of Goulburn and Penrith could be lost by swings of 6.6% and 5.2% respectively, the Daily Telegraph reported on Monday.

The seats polled in three rounds have shown swings against the Coalition government, indicating results too close to call or a loss.

A key issue is voter unhappiness over the stadiums issue, the polling shows.

The YouGov Galaxy poll canvassed 531 voters in Goulburn and 550 voters in Penrith.

Australian Associated Press contributed to this report