Research published online in the Society for the Study of Addiction, shows how researchers from Imperial College London and the University of Bristol, used statistical modelling to estimate the number of crack cocaine users aged between 15 and 44 across London.
Dr Matthew Hickman, from Imperial College London, and an author of the paper, said: "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. We must be cautious but the analysis suggests there is a substantial problem.
"With almost 60 percent of crack-cocaine users also opiate users, part of the increase in use is driven by heroin users, which has implications for treatment and prevention"
The researchers looked at data for 12 London boroughs from a number of sources reporting crack cocaine use, including numbers in specialist drug treatment, arrested, accident and emergency and community surveys, and the numbers of injecting drug users.
They identified 4,117 crack users, and using statistical modelling estimated there were a further 16,855 users who were not observed on one of the data sources, taking the total number to 21,000 for the 12 boroughs. The researchers then multiplied the numbers from the 12 boroughs to take into account the whole of London, and estimated 46,000 users aged between 15 and 44, accounting for 1.3 percent of the population.
The study also suggested that crack cocaine use was more than three times higher in men, at 2.4 percent, compared with 0.7 percent in women.
Dr Vivian Hope, from Imperial College London and an author of the paper added: "Although these results are only estimated figures, they do indicate the crack cocaine problem in London may be much larger than we initially thought, with our estimates almost four times higher than population surveys suggest. 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."
The study was funded by the Home Office Research and Statistics Directorate.