Chris Unwin from the Cider Press on the Barbican has made surfaces ridged, sloped or covered in vaseline, to make it difficult to cut or inhale cocaine from them.

He said: "You can't stop them using a coke spoon, but we have done as much as we possibly can.

"When they legalise these things I shall be first in line to sell it, but until that time it's against the law and it causes licensees a headache."

However, his efforts have not been appreciated by everyone and soon after the toilets were altered, someone set fire to them.

Chris Unwin said other licensees need to be careful to avoid drug users damaging their businesses.

Gangs fear

He recommends they use other people to help them spot potential problems.

He said: "It's very easy to slip into the feeling that everything's great, but you can often do with a fresh pair of eyes coming in.

"Even if it's a mate coming in just once a month to keep his eye on things because other people are expecting you to look at them, but they are not expecting an outsider to look at them."

Fears were raised in August that organised criminal groups from cities such as Liverpool are travelling to Plymouth to sell drugs.

Police believe they are attracted by high prices for drugs like heroin, which sell for double the price in Plymouth compared with other parts of the country.