Legal figures claim there has been a spike in "inappropriate police interactions with the trade" over the past year and claim Police Scotland are "using unlawful bullying tactics to get their way".
The main complaint is that police are appealing to licensing boards to have premises shut without making specific allegations or detailing their intelligence. It is claimed officers have demanded that staff hand over documentation, ranging from training certificates to bank statements, on weekend nights without explanation. It is even alleged officers have sniffed bottles to test the legality of spirits.
A recent abandoned court case involving a Glasgow licensee who faced prosecution for serving two undercover officers just one roll and sausage was also cited.
A key concern is the lack of training frontline officers receive on licensing despite its priority for the police. Senior police officers have admitted at a conference on licensing in Glasgow that there are issues with having officers trained to deal with a myriad of licensing laws.
It was also claimed they are also having to cope with different policing cultures being brought together under the single force.
A Police Scotland spokesman said it "welcomed comments from licensees with specific concerns", adding that its officers had "a long-standing good relationship with the licensed trade".
Licensing lawyer Janet Hood warned many of her clients felt their relationship with the force was changing for the worse. She said trust was evaporating amid concerns officers were trying to meet set targets.
She said: "Why do officers choose Friday and Saturday nights to make inquiries rather than a reasonable time when business isn't affected? Staff are being frightened and customers put off.
"Why do staff feel frightened of the police? It's because of their manner. They're wanting to see personal financial information, things like bank statements. What can they tell from that? The police should be taught the law, they should be reminded of their ethical code and they should stop treating the trade as if they were criminals." Archie MacIver, a prominent licensing lawyer and chairman of the Law Society's licensing committee, said complaints about the police approach to the trade were being discussed with increased regularity.
He said: "Concerns are being expressed that the level of training given to beat cops is wholly insufficient given the complexity of ever-expanding legislation."
Conference organiser and sometime government licensing law advisor Jack Cummins told delegates: "Police intelligence is a problem in my experience, where its a case of 'we have information on your client's premise but won't tell you'. You can't table information at licensing boards like that.
"To be brutal, the level of training for police officers on licensing law is extremely poor."
Police Scotland's Inspector Alan Morris told the conference it was "quite clear" training needed to improve, adding: "No doubt it will take time to get them as knowledgeable as we'd like them to be."
Police Scotland welcomed the comments. A spokesman added: "Our officers have a long-standing good relationship with the licensed trade and are committed to continuing this in the future.
"In the past year just one licensing lawyer has made a specific complaint to us."
He added that officers were not set individual targets.