Jacinda Ardern has given more detail this afternoon on what she intends the second wave of gun legislation to look like.

The Prime Minister announced the second tranche of proposed gun laws in July. It included the creation of a gun register, dropping the length of gun licences from 10 years to five and police being given additional powers to put warning flags over people.

1 NEWS was leaked a draft version of the legislation in August.

The registry would work in a similar way to vehicle registration, holding the name of the owner, date of birth and address, as well as the firearms licence number. It would be available both online and include a paper-based option.

Transfers, sales, purchases, imports, and exports of firearms would be recorded, with private sales still allowed.

The new warning flags system to show a person not to be 'fit and proper' to hold a firearm would consider: encouraging or promoting violence; hatred or extremism; serious mental ill-health issues including attempted suicide; having had various offences under the Wildlife Act, being a risk to national security and being involved in drug abuse or having a temporary protection order.

Ms Ardern said the Christchurch terrorist attack on March 15 "exposed weaknesses in legislation which we have the power to fix, we would not be a responsible Government if we didn't address them".

"The bill includes a register to track firearms and new offences and penalties that can be applied extra-territorially for illegal manufacture, trafficking, and for falsifying, removing, or altering markings," Ms Ardern said.

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"Every person who is currently found guilty of selling or supplying a firearm to an unlicensed person is liable for a term of imprisonment not exceeding three months or a fine of $1000. This bill will increase those penalties to two years and $20,000 respectively."

A Firearms Advisory Group will also be created to implement the rules of the Arms Legislation Bill.

"Our focus since March 15 has been on ensuring that our communities are as protected as they can be from the potential for another attack like the horrific one we witnessed in Christchurch," Ms Ardern said.

If passed, the new law would create a licensing regime for clubs and ranges, requirement for a licence to buy and hold parts, magazines and ammunition.

Health practitioners would be able to notify police with concerns of a firearm holder's health or wellbeing.

Regulations around advertising of firearms and ammunition is also set to be implemented.

The first reading of the proposed law will be on September 24.