© Associated Press/Haraz GhanbariA colony of honeybees
Millions of insects could be wiped out because thinly staffed inspectorate does not know where half the country's beekeepers are

A deadly Asian parasite that threatens to wipe out millions of bees across England and Wales has become endemic because Whitehall does not know the location of more than half the hives in the country, the National Audit Office reveals today.

The auditors estimate that at least 20,000 beekeepers are unregistered, which means they are never inspected and no action can be taken to eradicate the parasite before it destroys the bee colony, the report warns. The registered number of beekeepers stands at 17,000.

Failure to act could wipe out the country's ยฃ100m apple harvest and seriously damage pear, raspberry, strawberry and runner bean crops because they are highly dependent on bees for pollination.

The Department for Environment, Food and Rural Affairs describes the pest as varroa, "a serious Asian parasitic mite of honey bees".

"The mites feed on both adult bees and [the] brood, weakening them and spreading harmful pathogens such as bee viruses. Infested colonies eventually die out unless control measures are applied," it says.

Even where beekeepers are registered, the number of inspections by the National Bee Unit is low. In the Lake District, Pennines, Durham and north-east England, just over three quarters of registered hives are not inspected every year.

The highest level of inspections is in south-east England, which includes 39% of Kent orchards checked for the disease every year. In Wales, nearly half the registered beekeepers are inspected.

The report says: "Increasing the number of beekeepers registered with the department depends upon inspectors and others, such as local associations, encouraging people to participate and the accessibility and ease of use of the web-based register.

"The National Bee Unit has no national strategy to encourage beekeepers to register. However, over the past three years the bee inspectors working in the eastern region have increased the number of beekeepers registered in BeeBase by around 1,000."

It reveals that there are only 37 bee inspectors in England and nine in Wales. The report says they spend most of their time visiting areas of high-risk outbreaks and training registered beekeepers rather than searching out colonies that have not been registered.

Treating the parasite has become more difficult as it has become immune to some chemicals. Some beekeepers are using oxalic acid - obtained on the internet but illegal to import or use in the UK - to kill off the parasite. The veterinary medicines directorate is considering licensing the product to make the fight against varroa easier.

Edward Leigh, the Conservative chairman of the Commons public accounts committee, said: "Action to stem the very high losses of honeybees in recent years crucially depends on a regime of comprehensive inspections and treatment of colonies. At the moment, this isn't being done."

Jane Kennedy, the farming and environment minister, said: "Improving bee health is a key priority and we will bring forward a strategy urgently following the recent announcement of an additional ยฃ4.3m funding."