A study of high net worth customers by Lloyd's insurer Hiscox shows many are dangerously underinsured and have little idea of the true value of their belongings.
The research compared 64 high-value homeowners' previous valuations against new ones given by an independent valuer.
The valuations showed that only one quarter (26%) of homeowners had adequate cover for their house contents.
High net worth customers were, on average, underinsured by 60% and 31% were undervalued by at least 100%.
The study was commissioned to follow up a similar survey last year which revealed only 27% of householders who collected arts and antiques had asked for a valuation in the past five years.
A further 35% had never had their contents valued.
Charles Dupplin of Hiscox said the results revealed how difficult it was for high net worth clients to judge the value of their home contents and the benefits of an independent valuation.
Hiscox clients who discover they are underinsured will have their sum increased but the premium will remain unchanged until the renewal date.