Customs officers are to test new equipment designed to scan all mailbags arriving in the UK from Jamaica.
Customs hopes scanners will detect drugs in the post
It is hoped the move will halt an alarming increase in the amount of cocaine sent to the UK in the post.
Airport scanners that can detect traces of the drug on people has virtually stopped so-called drug mules travelling between the two countries.
So customs officers are to trial a new neutron scanner capable of testing entire mailbags for cocaine.
UK Foreign Office Minister Bill Rammell told BBC Radio 4's Today programme: "I think it's part of the solution. When you're dealing with the drugs industry, it's ingenious, it's illegal and well resourced.
"When you block off one route, they'll find another."
Despite the success of efforts to stop people smuggling in cocaine themselves, supplies of cheap crack on the streets of the UK from the Caribbean has continued to rise.
Police and customs officers say they are detecting larger quantities in the post; either sent via airmail, or using fast parcel services.
Nearly all crack cocaine on the streets of Bristol is estimated to have come from Jamaica and two large parcels were intercepted in January.
Detective Chief Inspector Neil Smart said: "Something that has come to our attention is the increased use of the postal service and couriers and we've become very successful in intercepting those packages."
Police in Kingston, Jamaica, said the cocaine was often sent in envelopes, and up to four kilos had been found in courier parcels.
Drug "mules" used to provide a way of sending cocaine to the UK cheaply and efficiently in person.
But measures including scanners introduced at airports in Kingston and in Montego Bay had contributed to the capture of smugglers.
In 2003, the number of cocaine couriers arrested in the UK had dropped by three-quarters, while the number arrested in Jamaica before boarding flights had doubled.
New figures due out next week are expected to show the number of people arrested in the UK after swallowing up to half a kilo of the drug has fallen from thousands per year to virtually zero.