Analysis of 2.6 million home insurance quotes between July 2015 and June 2016 has found that property owners typically estimate the value of their contents at £35,000.

However, according to MoneySuperMarket data, the average three-bedroom family home in the UK has £55,000 worth of items – meaning an insurance shortfall of £20,000.

The most common possessions itemised include in home-owners’ policies include laptops (34%), followed by bikes (23%), jewellery (22%), watches (7%) and TVs (2%).

The price comparison site also warns homeowners that items stored in gardens, garages or sheds aren’t automatically included on home contents cover.

It found items stored in outbuildings can be expensive to replace – sound systems left in the back yard are worth an average of £368, while the average Brit has £138 of booze in the garage.

Londoners have £265 of outdoor heating equipment in their gardens, while those living in Cardiff have up to £298 of liquid assets in the form of fish, rockeries and water features. And for those living in Norwich, the average BBQ is worth up to £290.

Kevin Pratt, insurance expert at MoneySuperMarket, said: “When insuring your prized possessions, it is crucial not to undervalue your home’s contents to get a cheaper policy. Otherwise you risk finding you’re not fully covered if you need to make a claim.

“As well as making sure you have enough overall contents cover, you should also ensure you itemise specific high value items on the policy – insurers want detail on any possessions likely to be worth £1,000 or more.

“Many policyholders are under the impression items kept in their garage or shed are included in their main home contents policy. However, if there is no connecting door to access through the main house, garages and sheds will usually be classified as ‘out-buildings’ and there will be a separate contents limit on most policies, as with items kept in the garden.”

He added that you should also check the terms of cover for items in the garden or garage as a bike might be insured while it’s in your garden, but only if it’s secured to an immovable object.