Allegations that a nightclub in Glasgow has secretly fitted a two-way mirror to allow male guests to spy on the women's toilets "as a bit of fun" are being investigated by police and council licensing officers.

Glasgow city council said it had received complaints that the Shimmy nightclub had installed a spy mirror – without warning female guests – between the toilets and a function room that was allegedly rented to private parties for £800.

A customer at the club called Amy told the Guardian she was warned about the two-way mirror by another customer when she visited Shimmy's recently to celebrate her birthday. Distressed, she left the toilet, and noticed that people in the club's main room could glimpse inside the toilets.

The main view into the women's toilets was from private booths that were immediately adjacent to the mirror, she said. "It was booked out by all boys and they were up against the mirror and making gestures up against the mirror."

Amy complained directly to G1 Group, owner of the recently relaunched club in central Glasgow, saying it was "absolutely outrageous" that women customers were having their privacy invaded, allowing men to "leer disgustingly" at them.

"Nowhere is it made clear that this is the case, so when visiting the bathroom for the first time, there are women bending over the sink, pouting into the mirror to redo their lipstick, adjusting themselves personally whilst unknowingly being watched by people on the other side," she said."What is even more vulgar is that the toilets face on to a private booth that can be booked out to specifically leer into the girls' bathrooms whilst the girls are unaware that they are being watched."

She received an email reply from Kirstin Nicol, G1 Group's director of risk and compliance, insisting a small disclaimer was printed on the women's bathroom mirror to warn that two-way glass was fitted.

"Firstly can I apologise that you have been offended, this is 100% not our intention at all. The mirror detail in the ladies' toilet was put in as a talking point, only the ladies at the sinks can be seen, there is another mirror behind the wall for people to use who don't like the one at the sinks. And there is no view of the cubicles or the corridor," Nicol wrote.

"We had attempted to put a graphic on the mirror to obscure it a little bit more but due to your comments we will change that and put a fuller one on it to make it more effective.

"I can assure you that if there was any behaviour deemed sexist or immoral or anyone was leering or making inappropriate gestures we would remove them from the club, and if necessary call the police.

"There is a small disclaimer on the mirror, however I will also look at making that bigger. We also have a toilet attendant who advises the ladies about the mirror.

"To date you are the first complaint, everyone else so far has seen it as we intended, as a bit of fun. We would have done the same with the male toilet, however structurally there wasn't the option."

The Scottish Sunday Express reported that several women had protested about the mirror after photographs appeared to show male guests with a clear view of women at a row of sinks.

A council spokesman said its licensing standards officers would visit the club. Police Scotland, the country's new single force, confirmed it was investigating after receiving a complaint.

The nightclub is alleged to have marketed the function room as part of a "smoke and mirrors" promotion. The Sunday Express quoted a G1 Group spokesman, Gary Hall, as saying it was definitely not the case that two-way mirrors had been installed.

No one from G1 Group or the Shimmy Club responded to calls and emails from the Guardian on Monday seeking a response. Complaints about the mirror allegations were being deleted from the club's Facebook page.

A council spokesman said: "The complaint is that mirrors have been installed, and licensing standards officers are going to speak to the licence-holders and see what can be done to resolve the situation. We have seen stuff on Facebook and so on, but the licensing standards officers have to be allowed to do their job and investigate what's happening."

A Police Scotland spokeswoman said: "We have received a complaint and the matter is currently being looked into."