Drugs gangs are taking control of sections of British cities such as Birmingham, Liverpool and Manchester, a United Nations drugs chief has said.
Celebrities 'normalising' drug use, as well as a widening gap between the rich and poor are among the reasons that "no-go areas are developing in certain cities, warned Professor Hamid Ghodse, president of the UN's International Narcotics Control Board (INCB).
Migration is another reason citied for the "vicious cycle of social exclusion, drugs problems and fractured communities" in certain areas.
Helping these marginalised communities with drugs problems "must be a priority", he said.
"Drug traffickers, organised crime, drug users, they take over. They will get the sort of governance of those areas.
"Examples are in Brazil, Mexico, in the United States, in the UK, Birmingham, Liverpool, Manchester, and therefore it is no good to have only law enforcement, which always shows it does not succeed."
Prof Ghodse called for such communities to be offered drug abuse prevention programmes, treatment and rehabilitation services, and the same levels of educational, employment and recreational opportunities as in the wider society.
"Youth of these communities must have similar chances to those in the wide society and have a right to be protected from drug abuse and drug dependence," he said.
He called for the problem to be tackled before communities reached their "tipping point" and it was too late.
"The consequences of failure are too high for society and should be avoided at all cost."
The INCB's annual report for 2011 found persistent social inequality, migration, emerging cultures of excess and a shift in traditional values were some of the key threats to social cohesion.
As the gap between rich and poor widens, and "faced with a future with limited opportunities, individuals within these communities may increasingly become disengaged from the wider society and become involved in a range of personally and socially harmful behaviours, including drug abuse and drug dealing," it said.
The report added: "While migration offers many positive benefits to the migrant and to society at large, it can create a sense of dislocation from the surrounding community and a sense of vulnerability on the part of those who are displaced.
"Where migrating social groups have travelled from areas associated with illicit drug production and drug abuse, there is a greater likelihood of individuals engaging in forms of drug misuse as a way of coping with such a sense of dislocation."
But the INCB warned none of the factors "should be seen as leading individuals inevitably into a lifestyle of drug abuse and criminality".
"Whatever the social processes and social pressures at hand, human beings still have the capacity to exercise some element of choice in what they do and what they refrain from doing," it said.
A Home Office spokesman said: "The Ending Gang and Youth Violence report published by the Government in 2011 sets out a comprehensive strategy for supporting local areas to reduce the effects of gang violence.
"We want to stop young people from joining gangs in the first place through intervention and support to children and families at risk of gang violence.
"This will be matched with tough and intensive enforcement action to bring perpetrators to justice."