"An unsavoury (amount) of the British population regularly enjoy a bite to eat in bed... with over 500,000 Brits washing their bedding just three times a year.

"It's estimated that 10 per cent of the weight of a two year pillow is comprised of dead skin and dust mites - so it's no surprise that your bed can become a minefield of bacteria, viruses, sweat and hair which can cause or exacerbate asthma.

"Beds are a prime habitat for dust mites."

She said America's Environment Health and Safety Online found a typical used mattress had anywhere from 100,000 to 10 million mites inside.

"Washing your bedding takes time and effort but to reduce levels of unwanted organisms and mites, you need to wash your bed linen at least once a fortnight - preferably once a week," she said.

Jacky Brown, of Sheilas' Wheels home insurance, which conducted the study, said: "With the cold weather making our beds more irresistible than ever, Brits are currently spending more than 49 hours a week sleeping in.

"The bed is one of the most used and expensive items in the home - so it's astonishing that more Brits aren't keeping it clean.

"With many beds being used as an alternative to the kitchen table for a place to breakfast or snack, it is crucial homeowners have accidental damage cover in the event of a major spillage."

She added: "The average person forking out up to £1,020 on their beds, an unpleasant 10 million(4) bed bugs and dust mites sleep alongside you every night."

Regions with the dirtiest bed sheets:

1. London (24 per cent)

2. North East (22 per cent)

3. South West (21 per cent)

4. East Midlands (19 per cent)

= 4. South East (19 per cent)

6. North West (18 per cent)

= 6. West Midlands (18 per cent)

8. Wales (17 per cent)

9. Eastern England (16 per cent)

10. Scotland (15 per cent)

11. Yorkshire (13 per cent)

12. Northern Ireland (8 per cent)

Note: per cent based on those washing their bedding just once a month or less frequently.