Housed in an isolated bungalow in the village of Meopham, near Gravesend, Kent, the laboratory was capable of producing a ton of amphetamines at a time with a street value of more than pounds 28m. If mixed with other substances it could fetch up to pounds 70m.
Eleven people, including two women, were arrested in raids on addresses in Kent, Surrey, London and the Isle of Man. Two were arrested at the drug factory.
Police seized more than two-and-a-half tons of chemicals that were in the process of being turned into drugs at the bungalow. They also discovered another building five miles away which they believe has been used as a narcotics factory in the past.
Large amounts of Spanish money have been found at another location, leading to speculation that the drug is being sold abroad as well as in Britain.
Amphetamine sulphate - commonly known as speed - which was found at the factory, is popular among youngsters, especially within the dance culture. It increases the user's energy and self-confidence and is becoming increasingly available throughout the country.
The discovery on Friday was the culmination of a 10-month investigation, code-named Operation Sweet, by officers from the South East Regional Crime Squad. Details of the operation were released only yesterday.
Officers found a vat with 20 to 30 gallons of chemicals boiling in a shed at the bungalow. In the loft there were several 50kg drums of chemicals. The factory made pure amphetamine powder.
Detective Superintendent Ray Hussey, from the Regional Crime Squad, said he was extremely concerned at how easy it was to obtain some of the chemicals.