The New South Wales opposition leader, Michael Daley, has given an “ironclad” guarantee he will not dilute gun laws if he is elected premier amid criticism over his party’s move to preference the Shooters, Fishers and Farmers.

The premier, Gladys Berejiklian, on Sunday called on the opposition leader to cut ties with the Shooters, saying Labor’s preference deal with the minor party legitimised its cause.

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

“I don’t stand for that, I never have and I never will, and I think the Labor leader and his party need to make the same call.”

Daley gave an “unequivocal and ironclad guarantee” that the state’s gun laws would not be weakened if he is elected premier on Saturday.

“Win, lose or draw I will not ever support the weakening of gun laws in NSW,” Daley told Sky News on Sunday.

He later told reporters a change to NSW gun laws would only occur if the coalition and the Shooters combined to weaken them.

He said he had not personally spoken with the Shooters, and preference deals were decided by Labor’s head office, not politicians.

Daley ruled out forming a formal coalition with the Shooters, or any other party, but would not rule out relying on them to form a minority government. “Well let’s see about that when we get to it,” he said.

Labor on Sunday announced it would build six ice detoxification and rehabilitation clinics throughout NSW at a cost of $100m if elected.

Daley also promised to spend another $100m to install solar panels on more than 350 schools.

“As we saw at rallies across the country on Friday, the next generation is demanding real action on climate change,” he said in a statement.

The education minister, Rob Stokes, said the government was already installing solar panels and battery storage in up to 1,000 schools across the state.

Meanwhile the coalition vowed to give police more powers to search the homes and cars of convicted drug dealers in a test program that will run across four police area commands.

The new court-issued drug supply prohibition order will give police the power to raid convicted drug dealers’ properties without a warrant if they have “reasonable grounds” to suspect there is evidence of a drug-related crime.

Berejiklian and Daley joined the prime minister, Scott Morrison, at Sydney’s St Mary’s Cathedral on Sunday afternoon for an interfaith service paying tribute to the victims of the deadly Christchurch terror attack.