London has a substantial problem with crack cocaine, researchers said on Monday, publishing a study which claimed one in every 100 Londoners aged between 15 and 44 could be using the drug.

Researchers from Imperial College London and the University of Bristol published research in the Society for the Study of Addiction, which said there could be 46,000, crack cocaine users in that age group.

“Although crack cocaine use has been a cause for concern in many countries since the 1980s, there has not been the predicted epidemic across the UK until now,” said Matthew Hickman, an author of the paper from Imperial College London.

“We must be cautious but the analysis suggests there is a substantial problem.”

The research was based on data from 12 London boroughs from a number of sources including specialist drug treatment centres, arrest numbers and accident and emergency departments.

Vivian Hope, another author of the report from Imperial College, said the results indicated the problem was much larger than previously thought.

“As crack cocaine use has been associated with increased risk behaviours, particularly among those who inject drugs, the high levels of use found are a concern.”

A spokeswoman for the London Drug and Alcohol Network who did not wish to be named told Reuters that crack cocaine had traditionally been a problem in big cities, especially the British capital.

“Crack has historically been a problem in London. I guess it’s relatively cheap and ... more widely available. Because of the effect crack has on people they may be in very chaotic lifestyles so in that sense it is very difficult to treat,” she said.