There's a call for a Government inquiry into why criminals are so heavily armed in New Zealand.

The Police Association is concerned about the number of criminals armed with guns.

This as a policeman was shot at while patrolling the streets of south Auckland early yesterday morning.

Police Association President Greg O'Connor said frontline police are disturbed at the number of criminals they stumble across with firearms.

"They're not necessarily armed to use them against police, they're using them to protect themselves from other criminals however police can become collateral damage in that."

Mr Greg O'Connor said we need to know what to do to curtail criminal access to firearms without punishing legitimate arms owners.

"But our criminal fraternity are increasingly armed, they are part of they're own arms race and we need to know why they are getting such easy access to firearms."