Hudson said the fact the document had been leaked showed there was concern within the Government about the changes.
"I'm worried about the path this Government is going down on gun reform," he said.
"The Government is using a big stick to achieve compliance by increasing many penalties … It shows they don't believe this legislation naturally encourages compliance."
Hudson said he was also concerned the legislation would see doctors dobbing in patients.
The draft bill includes a section that requires health practioners to consider "as soon as practicable", telling police if they think a patient who is a gun owner is unfit to own a weapon.
It gives doctors permission to pass the patient's records to police without threat of civil or disciplinary action - as long as it's done in good faith.
Hudson said that could lead to patients avoiding seeing doctors about mental health issues.
"This risks driving mental health issues underground by discouraging people from seeing their doctor about such sensitive issues," he said.
Police Minister Stuart Nash would not confirm or deny which parts would be in the final version.
"What I would like to know is if the National Party is going to support what we're doing," he said.
The broad contents of the bill had been clearly signalled in the Government's July announcement, Nash said.
"If there are any gaps I expect the Select Committee to identify and work through these issues."
The second tranche of changes publicly announced includes:
• A national gun register to record every firearm and firearms licence holder in the country, which would take five years to put in place.
• A higher test for licence holders to get and retain a licence, including warning flags that would be grounds for police to revoke a licence and confiscate guns.
• Licence holders will be disqualified if, in the previous 10 years, they
have convictions for serious crimes such as violence, gang activity, misuse of drugs,
firearms offences, or having a protection order made against them.
• Requiring a firearms licence to buy ammunition, magazines and gun parts.
•Tighter rules for gun dealership licences, requiring excellent character and sound technical capability.
• A new licensing system for the 260-odd shooting clubs and ranges, with ongoing monitoring.
• A ban on having visitors buying a gun in New Zealand, though hunting visitors may bring their own and register it, or lease one.
• Tighter rules on gun advertising; there are currently no restrictions.
• New offences and higher penalties for breaking the rules.
