A report by the German Press Agency (DPA) - reprinted in several national papers - said the quality and quantity of donations in the UK was so low that the Human Fertilisation and Embryology Authority was considering looking elsewhere for stocks for artificial insemination.

The HFEA dismissed the report as "nonsense" and claimed British sperm was just as potent as that of any other nation.

However, it did admit it was considering one bulk import from Denmark - for use in a clinic in Glasgow.

DPA journalist Friederike Rosenstock wrote that a "national study" had found that the quantity and quality of semen from donors in the UK is too low to fulfil the needs of British women seeking artificial insemination.

She wrote: "British men are no longer living up to expectations - according to a national study, their fertility is lower than ever before.

"As a result (authorities) on the island are even considering mass imports of sperm from the Continent."

Birmingham bottom

Germans are proud of their sperm

The worst quality sperm, she wrote, was in Birmingham, where just 25% came up to scratch.

Two-thirds of the sperm produced by Londoners was sub-standard.

Sixty per cent of the samples from the red blooded men of Southampton, however, made the grade.

The report blamed the supposed poor quality of British sperm on tight clothes, a sedentary lifestyle and central heating.

It suggested that Finland, France - and, unsurprisingly, Germany - would be ideal sources of more potent semen, as men there were more active and spend more time in the open air.

Dr Richard Petty, of London's Wellman Clinic, was quoted as saying: "Britain's men spend more time than ever before sitting on their backsides in the office, in the car or in front of the television.

"They also warm their testicles with elasticated underpants, instead of keeping them at least 2.2C cooler than the rest of their bodies."

Dr Petty suggested British men take a short walk in the fresh air and opt for less thick underpants.

Berlin daily paper Die Tageszeitung suggested that the supposed imports would threaten the future of the British nation as much as the invading armies of history.

"After surviving the Vikings, the Normans, the Romans and Hitler, Great Britain is threatened by another invasion," it said.

'Nonsense'

HFEA spokesman Barney Wyld dismissed the claims: "This is all a lot of nonsense. I don't know of any study that backs this up.

"There has always been a demand for more sperm donations, but no more so now than at any other time.

"I'm not aware of any evidence that sperm counts have been dropping in the UK or are any different here than from any other country.

"We are considering a single application to bulk import sperm from Denmark to one clinic in Glasgow, which has already received considerable publicity, but we are not considering mass imports of sperm from Finland or Germany or anywhere else."

Andreas Albrecht, of DPA, said that there had been no intention to offend British men and said the "study" was not an official report, but had been compiled originally by a British newspaper.

He said: "The article was intended to be light-hearted - written with a wink of the eye.