An investigation by BBC Radio Five Live has discovered evidence that people identified as almost certainly transporting drugs are still being allowed into the UK.

The investigation found that traffickers are exploiting a system which can only process a certain number of suspects at a time.

Immigration officers carry out health checks and x-rays on people coming into the country - if they find evidence that drugs are hidden inside somebody's body, the information is passed on to the customs service.

But the Immigration Officers' Union says often no action can be taken because of chronic underfunding.

'Massive problem'

Detective Inspector Bruce Ballagher, from Avon and Somerset Police, said more must be done to halt the drug smugglers at customs channels in terminal buildings.

He believes the best place to trap contraband carriers is as they walk through the "one-metre" gap at airports.

Mr Ballagher said: "It's not rocket science to detect smugglers coming through a gap a metre wide."

Mr Ballagher said: "We have a massive problem in the South West and just simple policing is not going to solve it.

"Hundreds of thousands of people come through Britain's airports every year.

"They all have one thing in common - they have all got to walk through a one-metre gap.

"The problem is a metre wide but its effects are huge... it is a funnel."

Force liaison

Police estimate there are 15-25 drugs couriers on each flight from Jamaica to Heathrow and Gatwick, each of them carrying approximately half a kilogram of pure cocaine, usually swallowed inside condoms.

Each courier's load is estimated to make �25,000 of profit.

But drugs also fuel crimes by addicts such as burglaries, robberies, thefts from vehicles, violence and intimidation.

Mr Ballagher said: "We are in liaison with other forces and airports, and have met the Jamaican High Commission, but perhaps resources should be looked at."

In Bristol, Operation Atrium has been tackling imported drugs and their effects in the South West for almost a year.

Police have arrested 238 people - 71 for supply offences - and another 50 have been deported.

Firearms, knives and other weapons have been seized as well as heroin and crack thought to have a potential street value of �500,000.