Almost half of prisoners addicted to drugs fail to complete rehabilitation courses designed to help them kick the habit, the Home Office has admitted.

Eight out of 10 arrivals at some inner-city jails have a serious drug habit and prisons are struggling to rehabilitate addicts already behind bars, Home Office figures indicate. Paul Goggins, a Home Office minister, said that of 4,703 inmates who started intensive drug treatment programmes in 2003-04, only 51 per cent finished them.