Southern district police last month began stationing plain-clothes officers in licensed premises to ensure licensees were complying with the Sale and Supply of Alcohol Act.
But that approach has raised the ire of the Hospitality Association.
''It's not appropriate for police to be spying on patrons,'' Mr Robertson said.
''If it wasn't so serious it'd almost be funny.
''They [licensees] can just as readily be inspected by a uniformed police officer. We think the public will find this abhorrent.''
Dunedin alcohol harm reduction officer Senior Constable Ian Paulin said the policy had not been used in Dunedin yet, ''but it will happen''.
''It's going to supply valuable information about what goes on in licensed premises,'' he said.
It would not result in a reduction in uniformed officers patrolling the streets and the officers who went undercover would be ''brought in from outside the area, not impacting local numbers'', he said.
It was not about trying to catch licensees in an underhanded manner.
''If they are doing a great job, that information will be fed back to the bars, so it will go both ways,'' Snr Const Paulin said.
Licensees were recently sent information about the policy and their obligations under the Sale and Supply of Alcohol Act.
The initiative would run until July next year, ''targeting risk times and risk events'', he said. Police first used the tactic in Queenstown late last month.
Otago rural prevention manager Senior Sergeant Allan Grindell said the initiative provided benefits which traditional police work could not.
''We will be able to observe the behaviours of patrons over a longer period of time and see how a licensee manages this behaviour,'' he said.
''Under the Sale and Supply of Alcohol Act 2012, there are new responsibilities on all of us to manage alcohol more safely.
"Our plainclothes staff will have a particular focus on intoxication in bars, but they will also note and observe activities surrounding host responsibility and security.''
If police saw intoxicated patrons and they believed it could amount to an offence or escalate into an incident of disorder or violence, a team consisting of police, council licensing inspectors and Public Health South would be informed.
Those operating within the law did not need to worry, he said.
''It's the expectation of police and our partner agencies that the aim of licensed premises staff must be to prevent patrons from becoming intoxicated or allowing them to remain on the premises if intoxicated.
''Premises operating ... within the law will have nothing to be concerned about.''
Hospitality Association Central Otago branch president Chris Buckley said he had not heard about any action being taken after the recent use of undercover officers in Queenstown.
But he felt the policy was ''underhanded''.
''It's a bit of a shame it's got to this,'' he said.
''I honestly don't care if they want to play like that, that's fine, they won't find anything.''
Dunedin City Council liquor licensing co-ordinator Kevin Mechen said it was ''a good idea'' and ''can only be positive.''
''For late night staff it's really up to them to make sure they are looking after the licensees' licence.
"But if they are doing everything right they have nothing to fear and if they aren't doing it right, they are tarnishing the name of everybody else,'' he said.
Hospitality Association Otago branch president Mark Scully said he did not want to ''protect members who break the law'', but there were better ways of targeting them.
