New X-Ray scanners at British airports could be exposing passengers to potentially dangerous levels of radiation, according to one senior radiologist.

The machines are designed to "strip search" passengers by using low-level X-Rays, which produce an image of their bodies, revealing whether they are secretly carrying weapons, explosives or illegal drugs.

But the scanners may not be safe for certain people, particularly children and women in the early stages of pregnancy, according to Dr Sarah Burnett, who works as an independent radiologist in London.

"It is illegal to expose people to any level of radiation without medical justification," said Dr Burnett, who raised her concerns after being asked to undergo a full-body scan at Luton Airport.

"So how is it that the Government is allowed to irradiate us willy-nilly at airports?

"I am particularly concerned about the potential effects on women in their first trimester of pregnancy.

"That is when the risks of the baby developing genetic abnormalities are highest because radiation exposure can damage the body's reproductive DNA."

Called the Rapiscan Secure 1000, the device looks like a big filing cabinet and fires a low-energy X-Ray beam over the body.

It has been trialled mainly at Heathrow, where four have been in use over the past couple of years.

However, it has already attracted controversy for producing revealing images clear enough to make out passengers' genitalia.

Indeed, U.S. airports have now refused to use them until the manufacturer can promise more privacy.

The X-Rays penetrate one-tenth of an inch into the body, enough to detect any devices or drugs hidden just under the skin.

According to Rapiscan Systems, the California-based company which makes the machines, each scan generates only three microrems of radiation - compared to 10,000 in a chest X-Ray.

The firm claims this is no higher than the amount that the body is normally exposed to every five minutes from "natural" radiation in the atmosphere.

The company also says that frequent flyers would need to have at least 5,000 scans a year before there would be any health threat.

What's more, it adds that longhaul passengers will soak up more so-called radiation during the flight, from the plane's equipment, than from the scan.

However, last year the Transport and General Workers Union investigated claims that five female security guards suffered miscarriages as a result of prolonged exposure to radiation from using the machines at Heathrow.

"The machines are referred to as 'low-dose', but there is a school of thought that there is no 'safe' radiation dose," said Dr Burnett, who has had 15 years' experience working in the NHS.

"It is true that passengers are exposed to 'cosmic' radiation within the aircraft, but there's nothing they can do about that - it can't be avoided.

"We can, however, avoid deliberately exposing people to radiation."

The British Airports Authority said passengers are free to refuse the X-Ray. But if they do, they will then have to be hand-searched.

Dr Gill Markham from the Royal College of Radiologists urged passengers not to worry, as the dose is so low it is unlikely to cause harm.

But women who think they may be in the early stages of pregnancy should tell airport staff if asked to have the scan.