Police are calling the first weekend under new alcohol laws a success, but Hospitality New Zealand says large crowds on the streets at 4am will need ongoing monitoring.

Under the new Sale and Supply of Alcohol Act, which came into effect on Thursday morning, bars and pubs must close by 4am.

Hospitality New Zealand president Adam Cunningham said the small amount of feedback from members indicated the weekend had gone well.

"There is some challenge in main centres around the volume of people on the street at 4am,'' he said.


"Obviously when you close all places at the same time especially in the Auckland and Wellington areas there's been a huge volume of people on the street.''

Mr Cunningham said crowds were monitored by a "very large contingent of police''.

"Is that the level of policing that's going to be required at 4am each weekend? It's not going to change in terms of the volume of people.''

The association had been focused on making sure members understood the rules in advance of Thursday's change, he said.

"Now it's just making sure that it's done as well as it can be for both operators and the safety of customers at that time of night.''

Police inspector Ben Offner said it was expected 4am crowds would decline as people adjusted their behaviour to the new laws.

"Hopefully we'll see a shift in habits around night time entertainment, and we won't expect to see so many people on the street at 4am.''

He said police would continue to monitor behaviour as people adjusted to the new law. "We're conscious of it and we're conscious that we want to make it as smooth a transition as we can.''

Shift commanders in Auckland and Wellington were very happy with behaviour last weekend, Mr Offner said.

"The sky did not fall and there were not hundreds of people on the street rioting.''

Police saw a drop in alcohol related harm events compared to previous December weekends.

Mr Offner said it was early days, but signs were positive that the legislation would reduce alcohol related harm.

Key law changes include:

* Off-licences must close by 11pm

* On-licences must close at 4am

* Police officers will be able to issue alcohol infringement notices for a range of offences including breach of alcohol bans, lending ID to an under-18, and presenting fake ID, each incurring a $250 fine.

* Bars that serve intoxicated people or allow them on the premise risk a fine of $10,000. Police will use an alcohol assessment tool to determine whether a person is intoxicated.