The drugs were said to have been found on the girls at Accra airport by Ghanaian Narcotic Control Board officers while trying to board a plane.
The officers were taking part in Operation Westbridge with HM Revenue and Customs (HMRC).
It is aimed at stopping traffickers getting drugs into the UK and Europe through the West African country.
Operation Westbridge follows the success of Operation Airbridge, a joint initiative between the UK and Jamaica to catch couriers carrying Class A drugs in their bodies, before they board planes from the island.
Tony Walker, leading the operation for HMRC, said the alleged use of such young girls as couriers "vividly illustrates the ruthlessness of the criminal drug gangs involved in this traffic".
Mr Walker added: "The Westbridge collaboration between Ghana and the UK is delivering real results in this and other cases by helping to protect both countries from the violence and corruption that always accompanies the trade in illegal drugs."
In the operation, which was launched last November, HMRC officers give technical and operational expertise to the Ghanaian government which includes training in the use of Foreign Office-funded scanning equipment.
A Foreign Office spokeswoman said: "We are aware of the arrest of two British national minors on 2 July at Accra airport. "Next of kin have been informed and we are providing full consular assistance."
She said the Foreign Office was unable to confirm any personal details due to the girls' ages.
HMRC confirmed the teenagers were arrested at Accra airport on 2 July, allegedly carrying an estimated £300,000 worth of cocaine.
Güncelleme Tarihi: 12 Temmuz 2007, 16:50