They were rushed through Parliament after the March 15 terror attacks, where a gunman murdered 51 people using automatic weapons.
Bridges said the first gun bill "stacked up" and was the right thing to do.
But the second tranche of laws – soon to go through Cabinet – seemed to be aimed at "good, law-abiding people rather than the crims [criminals], the gangs and the extremists", he said.
The second tranche would put in place a national gun register, tighter rules for gun dealership licences and put in place higher penalties for breaking current gun rules.
Asked if National were playing politics by indicating it would not support the bill, Ardern said: "I would hope not."
"This is about safety," she said.
"I would like to think the vast majority of New Zealanders, including law-abiding gun owners, would agree with that."
Police Association President Chris Cahill said he was concerned with National's decision.
"I hope that all politicians, including National Party politicians, see the suite of firearms reforms as a once-in-a-generation chance to rid our communities of assault weapons and deliver transparency with respect to how many weapons we have in New Zealand."
He pushed back on Bridges' claim that the second tranche would be detrimental to law-abiding citizens.
"This process is not about punishing the vast majority of firearms owners who are law-abiding citizens.
"It is about making our communities safer and ensuring fair compensation for those who now need to give up certain firearms."
