The two, both from London, were stopped by Ghanaian drug officials on July 2 and arrested on suspicion of drug trafficking, said Tony Walker of Britain's HM Revenue and Customs.
Both are receiving guidance from consular officials, a Foreign Office spokeswoman said in London.
Walker said the girls are believed to be drug mules - couriers who transport cocaine for traffickers. "The use of such young girls as couriers vividly illustrates the ruthlessness of the criminal drug gangs involved in this traffic," he said in a statement from London.
With cocaine prices in Europe soaring, West Africa has become a new drug trafficking route. Cocaine, originating mostly in Colombia, is brought on small planes and dropped off on islands off the West African coast, and then distributed to mules who carry it onward to Europe.