The price of cocaine has fallen to a record low as a United Nations report says that celebrity users have made the drug socially acceptable.

Police say privately that cocaine is becoming as acceptable in middle-class Britain as cannabis was a generation ago and that they are losing their battle against the drug.

The UN drug control agency’s annual report, published today, puts the blame at the door of celebrity culture and accuses the police of turning a blind eye to the rich and famous who misuse the drug.

“Celebrity drug offenders can profoundly influence attitudes, values and behaviour towards drug abuse, particularly among young people,” it said. “The authorities should ensure that celebrities who violate drug laws are made accountable.”

The criticism comes after widespread media coverage of the drug problems of the singers Pete Doherty and Amy Winehouse. Keith Vaz, chairman of the Commons Home Affairs Select Committee, said that he would launch an inquiry. “It is vital that we look at the law governing drugs and their availability in the light of this information,” he said. “We need to be tough on the use of drugs, especially by those who may be seen as role models.”

The UN report says that Britain, Spain and Italy have the highest levels of cocaine misuse in Europe and warns that West Africa is becoming a hub for traffickers. The drug is smuggled out of Colombia through Brazil and Venezuela to countries such as Benin, Cape Verde, Guinea-Bissau, Mauritania and Senegal on board ships, private yachts and private aircraft. It is then repacked in smaller quantities and smuggled into Europe by air. The main airports used are Dakar, Conakry, Freetown, Banjul, Accra and Lagos.

Hamid Ghodse, a member of the UN’s International Narcotics Control Board, said that most of the cocaine from West Africa entered Europe through Spain and Portugal, with smaller amounts direct from the Caribbean.

“The organised criminal gangs have lots of resources, they have lots of power,” he said. “They never get near the drugs themselves and therefore operate with impunity”.

Government figures show that the average cost of a gram of cocaine on the streets has gone down from £71 a decade ago to £45 last year. Harry Shapiro, of the charity Drugscope, said: “Consumers are being given a two-tier market. They can buy lower quality cocaine for £30 a gram or pay £50 to £60 for higher quality cocaine.”

The UN report also expressed concern about opium production in Afghanistan. Professor Ghodse said that he believed that the international forces there had lost control. Production rose to 8,200 tons last year.

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