A senior Sussex policeman has written to the Jamaican police commissioner to help officers on the island stamp down on the drugs trade into Gatwick.

The move is part of a continuing campaign by police, Customs and Excise and airlines against drug smuggling at the airport.

The problem was highlighted this week by Phil Sinkinson, British Deputy High Commissioner in Jamaica, who claimed one in ten passengers arriving at Gatwick and Heathrow from Jamaica were smuggling cocaine.

Mr Sinkinson estimated up to 30 kilos could be brought in on each plane hidden inside drug couriers, or "mules".

With four British Airways flights a week arriving at Gatwick from Kingston, this could mean 120 kilos coming into the airport with a street value of £6 million.

Chief Inspector Mike Alderson of Gatwick Police said: "We are working very closely with our Customs colleagues and we have close arrangements with the Jamaican authorities.

"Arresting smugglers is very much a Customs function, but we work closely to support them. The other thing we are doing is we are in direct communication with colleagues in Jamaica looking at ways in which we can improve our practices, intelligence and evidence gathering."

Chief Insp Alderson said the police became more involved with crimes leading on from the actual smuggling rather than the smuggling itself.

"Most of the stuff comes via the Customs route. For us the issue arises when, for example, someone says they have been forced to carry drugs.

"We have had a number of those in the last six months and as a result of that I have written to the Commissioner in Jamaica.

"The way we gather evidence needs to be in a usable form for the Jamaican authorities because if someone says they are acting under duress that crime will have taken place in Jamaica."

Chief Insp Alderson said in some cases people's families had been threatened if they refused to smuggle drugs.

Only last month 16 people were arrested at Gatwick when they stepped off a plane. Drugs with a street value of more than £250,000 were recovered. The seizure was the result of a routine Customs check.

A Customs spokeswoman said: "Less than ten per cent of cocaine which is seized by Customs arrives from Jamaica. What we are talking about is one way in which people smuggle drugs and during the last financial year Customs at Heathrow and Gatwick detected more than 400 couriers.

"At Heathrow and Gatwick they have developed a great deal of expertise in identifying and catching drug smugglers."

She said Customs devoted the amount of resources in proportion to the risk of smuggling and the type of smuggling and they kept this under continuous review.

"In addition to what we do on the ground we do checks on particular flights. It can be a mixture of both random checks or on evidence received."

Metropolitan Police and Customs, assisted by Sussex Police at Gatwick have been running Operation Trident since March 1999 to combat the problem. The initiative primarily targets gun crime in London, but this is often fuelled by drugs which arrive at Gatwick.

The airlines are also working closely with Customs to help stop trafficking.

A British Airways spokeswoman said: "We co-operate with any initiatives. One of BA's conditions of carriage is we reserve the right to refuse to carry people if they are or we have reason to believe they are in unlawful possession of drugs."