Late-night cafes, bars and clubs have been caught selling alcohol to children as young as 16 in an undercover police operation thought to be the first of its kind in the country.

Sussex Police used teenage police cadets to try to buy alcohol from a number of city centre venues in Brighton and Hove with alarming success.

Four of the six venues that the operation targeted sold alcohol to underage customers on Saturday night.

The operation was launched in response to intelligence received by police over a number of worrying incidents including ongoing police investigations into sexual assaults of underage girls in at least two Brighton clubs.

The licensing team also received reports that a drunk student of 15 was able to buy a bottle of Johnny Walker whisky for £60 at a late-night cafe above a restaurant.

Searches on Facebook sites of clubs have also revealed underage customers tagged in to photographs of nights at the venues.

The intelligence led operation focused on nine city centre bars, late-night cafes and clubs including some of the city’s most prominent and popular night-time venues.

Jean Irving, force licensing and public safety manager for Sussex Police who led the operation, said it was important to protect the city’s children from harm as well as ensuring that managers of late-night venues are meeting their licence conditions and objectives.

She said: “Our intelligence indicates there are a lot of under 18s who get in even though these premises are supposed to be observing a Challenge 25 policy where door staff should be checking the ID of anyone who looks 25 or under.

“There are so many premises in the city, we never do these test purchases on an ad hoc basis.

“But intelligence does not guarantee success, I have been on test purchases where there have not been any sales.

“We are finding that it’s not necessarily the big venues that we are having the problems with, it is the smaller, out-of-the-way places that we are getting reports about.”

Four police cadets were used in the operation accompanied by a number of plain-clothed and uniformed officers.

Cadets were told to order bottled beer or alcopops following a recent attempt by pub owners caught out by a test purchase operation.

The pub’s management later claimed in court they knew it was an underage customer and had served a pint of coloured water rather than a pint of beer.

Ms Irving said that Saturday’s operation was not designed to use underhand tactics to catch out venues.

She said: “We are not doing anything to make the cadets look older than they are. They are told to dress normally as they would if they were going to a party.

“The children have been told they must state clearly that they have no form of identification and if door staff insists upon ID then the whole group leaves.

“We know that in reality when kids try and buy alcohol they are not going to say 17 so our cadets were allowed to lie and to say they were 18 but we chose not to give them fake IDs.

“Officers will also visit every venue we have tested either tonight or in the next few days and we will be letting them know that we have been checking their operations. We are very open and honest about it.

“Obviously if they have sold to underage customers then we will be letting them know about as soon as it happens but we will also be letting them know if they didn’t sell.”

As the operation was the first of its kind, Ms Irving drew up the operation note completely from scratch.

She said her main priority was that the cadets on the operation were safe at all times when going into the alien environment of late-night clubs and bars.

She said: “We had more officers involved in the operation than we would with a normal test purchase operation in an off-licence because of the need to protect these young children going into this sort of environment.

“With the best will in the world we know that in clubs you have drug dealers and other dangers and that’s why when we are going into the bigger venues we are going as a group even though that might make them less likely to get in.”

Of particular concern for the licensing team flagged up during the investigation was the fact that at least one bar staff employee could not speak English.

Ms Irving said: “How can they be promoting their licence objectives if they can’t even speak English?

“How can they check if someone is old enough, how can they tell someone they have had too much to drink?

“If we try and put conditions on their licence about speaking English people might complain that’s racist but how can you carry out your objectives if you can’t communicate.”

The offending venues are set for talks with the licensing team over the next few days.

The worst offenders could have licence reviews which could result in venues being instructed to improve staff training, possible installation of ID scanners and change their age verification policies.

Ms Irving said: “We need to break the chain.

“Kids know they can go to this place and get served alcohol and then will tell other kids.

“They are all telling each other ‘go here because they don’t care about serving underage’. That is what the teachers are telling us.”

Councillor Stephanie Powell, chair of Brighton and Hove City Council’s licensing committee, said: “We have a lot of licensed premises in Brighton and Hove and they are an important part of the local economy.

“Our licensing and trading standards teams work closely with Sussex Police to support businesses in preventing crime, disorder and public nuisance.

“Protecting children from harm is a key licensing objective, and regular test purchase operations are an important part of our work.”