Burglars benefit £750 million from homeowners who leave keys lying around an empty house, according to an insurer.

Norwich Union research reveals each household is carelessly offering thieves on average £2,405 worth of contents and cars by not taking better care of valuable keys

Some 80 per cent of homeowners have up to five sets of keys in their home, half of all people keep them all in one place and one in eight people give burglars a helping hand by labelling their keys.

If keys are kept within sight or reach of windows and doors, burglars use 'smash and grab' tactics that take a matter of seconds or some opt for the 'hook and cane' method – fishing for keys through letterboxes or cat flaps with a hook or magnet attached to a stick.

"Homeowners should ensure all windows are shut when ever they leave their house. When on holiday, the house should be left secure and we would advise limiting the number of people who know your home will be left empty for this period of time," said Paul Redington, claims manager from Norwich Union.

"Most importantly, lock car and spare keys in a secure place during you holiday."