Judith Collins says the gun law changes announced on Thursday don't go far enough.
But the Government's saying its crackdown is just the beginning.
As of 3pm Thursday military-style semi-automatic weapons have been re-categorised, making them legally unavailable to most gun licence holders. Next month legislation outlawing the guns permanently will likely pass with near-unanimous support in Parliament.
"Move quickly to get this through in urgency," National MP Collins told The AM Show on Friday.
"The National Party will support you. We will get this through and we need to sort this out."
Something the legislation doesn't create is a national gun register, which Collins says is essential.
"I think they could go further... Police at the moment have no idea how many guns someone has, and the closest thing they have as an indication that someone has guns is whether or not they've got a gun licence. Lots of people have gun licences and have never used them."
Registering firearm serial numbers was one of the recommendations made by the Law and Order Select Committee following its look at the country's gun laws in 2017. It was rejected by then-Police Minister Paula Bennett.
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Collins said the reason was the timing of the 2017 general election.
"What happened is some of those were adopted, and then nothing happened after that because legislation needed to come in and there was an election and it was dropped. There has been a lot of work done - let's just understand now is the time to get everything done."
Labour MP Kris Faafoi, appearing on The AM Show with Collins, said a gun register will definitely be looked at.
"The change that was announced at 3pm yesterday is just the beginning, but a rather important beginning, to the gun reform that is needed in New Zealand."
He praised officials' work in getting the legislation ready only six days after the Christchurch mosques attack, which left 50 dead.
"A lot more has happened in the last week than has happened for decades... Those are the kinds of issues we will continue to look at... There is more change planned ahead."
The gun lobby looks likely to drag out proposed changes. Council of Licenced Firearms Owners spokesperson Nicole McKee, appearing on The AM Show before Collins and Faafoi, backed the sales freeze but said more time was needed to consult with the firearms community.
"We need to support our Government where there's going to be an effective change that will stop this happening again, but it does need to have thorough consultation," said McKee.
Collins said she's already being inundated with messages from the "more extreme end of the gun lobby".
Host Duncan Garner suggested she tell them to "bugger off".
"Oh yes, I think so," she agreed. "We have people with immense commercial reasons to encourage this sort of trade... We will support the Government to get what they need to get done."
'Make sure that good comes from this'
Faafoi, who is from Christchurch, said he met with leaders of the Islamic community on Wednesday.
"I was inspired by their strength and their hope something good had to come from this. I can't imagine what torment and hurt they're going through at the moment," he said.
"The fact there's been an outpouring of love and understanding and a sharing of grief from right around the country, from nearly every corner of New Zealand regardless of faith or race, is inspiring. We all need to take a signal from them about how they've responded to this, to make sure that good comes from this."
Collins said we need to understand Muslims are New Zealanders too.
"Islam has been in New Zealand since 1850. People should not look at someone who is Muslim and think, 'you're a new immigrant'. Many have been here for generations.
"Everyone in New Zealand should be able to go and practise their faith whenever they want to in safety... This is a liberal democracy where people are free to go about their business."