Investigations into the decimation of bee colonies have been stepped up after more severe losses this year, the government said on Friday.

More than 25 percent of colonies were found dead, compared with 18.2 percent in the same period last year.

"While it is not unusual to see some losses over winter, there are early signs of significant colony losses across the country, which are being investigated," said the Department for Environment, Food and Rural Affairs (Defra).

"As a precautionary measure, work on the investigation of bee colony losses by the National Bee Unit (NBU), which commenced last year, is being given higher priority."

Bee colonies in the UK have already suffered under the impact of the parasites varroa and nosema spp.

Losses in 2007 were linked to the Asian parasitic mite varroa while laboratory investigation of samples collected from dead or dying colonies in the summer indicated high levels of the parasite nosema spp coupled with viruses, particularly the chronic bee paralysis virus.

Bee inspectors, who have checked 3,000 fewer colonies this year because of the weather, fear there may be other reasons for the losses.

"The position this year may be different given that the wet weather experienced in summer 2007 meant that bees were confined to their hives for long periods and were therefore unable to forage for sufficient nectar and pollen to sustain them over winter," Defra said.

The unit is looking into whether there is a link with a dramatic fall also seen in the US, although there is no evidence yet that the situation is the same.