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.

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."