Vespa velutina, which preys on honey bees, is already spreading rapidly across mainland Europe and could pose a serious risk to the UK’s apiculture

Beekeepers have been told to be alert for invading hornets that have killed six people in France and could pose to serious risk to Britain’s honey bees.

The Asian hornet, which preys on honey bees, is spreading rapidly across France and other parts of mainland Europe, and there are fears its arrival in Britain is only a matter of time – particularly in light of the unusually warm spring weather.

The hornets’ sting can cause deadly allergic reactions in humans but officials are particularly worried about their impact on the crucial ecological role played by honeybees, and the possibility they could permanently affect Britain’s biodiversity.

A spokesman for the Department for Environment, Food and Rural Affairs said: “It’s not great news for bees because they are not a friend to the humble honey bee, and that’s why we don’t want them here.”

The hornets, known to entomologists as Vespa velutina, are smaller than their native European counterparts, which are brown and brownish yellow, according to the National Bee Unit, a Defra agency.

Unlike Britain’s native hornets however, they are specialised predators of honey bees, raising fears they would be detrimental to fragile populations that have already suffered years of decline.

Tim Lovett, the public affairs director of the British Bee Keeping Association, said his members “could do without it, but I don’t think it’s ‘disaster strikes’”.

“We already have very variable weather, other diseases for which we don’t have great answers and there’s also this question of pesticides,” he said.

Concerns about Asian hornets came up around this time every year, Lovett said, as the NBU holds meetings with beekeepers across Britain to discuss potential risks the summer might bring. They appeared regularly on the agenda, he said.

Defra has issued advice to beekeepers to keep an eye out for the invaders so the department can take prompt action if any are spotted. “If they do spot a hornet we want them to tell us, then we will get rid,” the spokesman said.

Defra also warns people not to approach nests, which are usually found high in trees and on buildings. Six people have already died of anaphylactic shock in France after being stung, reports claim, including one man killed in the Loire valley by a swarm from a nest he had disturbed.

Experts however downplayed their danger to humans. Lovett said “one man’s bee sting is another man’s itch”, while Paul Pearce-Kelly, head of invertebrates at the Zoological Society of London, said he did not think Asian hornet stings were any worse than those from normal wasps or bees.

The Natural History Museum’s Hymenoptera curator, Dr Gavin Broad, said in a briefing published last year: “For most people, it hurts when you’re stung, throbs for a few hours and then dies down. Hornets do inject venom, however, so it you’re allergic to wasp stings, your reaction would probably be similar and likewise treatable with antihistamine.”

Queens build their nests in April and rapidly begin to lay eggs until the population reaches about 6,000 individuals. By July, the hornets begin hunting honey bees, chopping them up and feeding them to their larvae, which need a particular mix of proteins to thrive.

According to reports, each Asian hornet can devour up to 50 honey bees a day, with swarms able to decimate bee colonies in just a few hours. Their bee hunting can continue well into November, according to the NBU. Lovett added that bees were able to defend themselves against the predators by surrounding them and stinging them to death.

Asian hornets were first spotted in south-west France in 2004, after apparently stowing away in a consignment of pottery which had arrived in Bordeaux from China. They have since colonised the whole of the west of the country and are also believed to have taken hold in the east.

Their presence was confirmed in Spain in 2010, and in Belgium in 2011. A 2012 NBU study says their arrival in Britain is very likely and warns that once established their spread will be rapid.

A statement from Defra said: “There have been no confirmed sightings of Asian hornets in the UK. We are aware of the potential impacts they could have on honey bees and have plans in place to remove them if they are identified. This includes comprehensive monitoring and teams ready to destroy any confirmed nests.”