Undercover police target pubs and clubs in Surrey
Plain-clothed officers will be targeting Surrey pubs which have problems with alcohol-related violence.
Insp David Hollingsworth, the new police chief in the borough of Elmbridge, said officers will spend time in a "small number of premises".
He said they would act covertly but the initiative was not about "monitoring private conversations."
However, a spokesman for an umbrella group representing licensees said it "smacked of Stasi-like activities".
Bill Sharp, of The Guild of Master Victuallers, said: "I think this will be undermining professional licensees.
"People are entitled to go to a public house and enjoy the evening, as long as they're not breaking any laws.
"You don't want someone sitting next to you writing everything down. Where does it stop?"
Mr Hollingsworth said some pubs in Elmbridge regularly had problems with violence and anti-social behaviour.
He said: "It's not about monitoring private conversations or actions, it's about going into premises to see if any offences are being committed.
"I don't think it's a moral problem at all. I have a duty to ensure public safety, and if that helps me do that, I will do it."