The haul of 5.7tonnes was seized with 11.3tonnes of opium, worth £141million, and 841kg of hashish valued at £3.3million.
During the operation last month, 63 terrorists were killed, ten armed insurgents and drug traffickers of national and foreign citizenship arrested, and 14 Afghan hostages released.
The raids took place with Afghan police in the Bahramcha and Haji Wakil areas of Helmand province, where British forces are based.
It was aimed at seizing drugs before they are exported and possibly make their way on to the streets of Europe.
Bomb and weapon making materials were also taken in the operation.
The drugs, along with 4.5tonnes of ammonium chloride used to turn opium into heroin, were burnt and two processing factories destroyed.
The heroin seizure alone was more than the entire amount seized during the first three months of this year.
Afghan interior minister Bismillah Khan Mohammadi said: ‘Our special counter-narcotics forces have brought a fantastic achievement to the people of Afghanistan.
‘The seizure of heroin represents the largest single seizure of heroin not only in Afghanistan but the world.’
Helmand’s former head of counter-narcotics Philippa Brown said the amount of the seized drug represented 25-30 per cent of Britain’s annual consumption of heroin.
‘We are making these seizures in conjunction with giving out alternative crops including wheat, grape and fruit trees to show that there is an
alternative to poppy cultivation,’ said Mrs Brown.
Opium seizures in Helmand are significantly higher than levels last year but prices for the drug have also risen sharply, British officials warned.
Bad weather, disease and insect damage have resulted in the cost of a kilogramme of raw opium rocketing from £29 to £142.