Many individual savings account (ISA) investors might have unbalanced portfolios, research has shown.
This suggests they pay little attention to the assets held in their ISAs, and leaves them open to big losses.
Bestinvest Brokers analysed ISA investment figures supplied by the Investment Management Association.
They concluded that ISA investors have too many UK shares, have too much invested in quality corporate bonds, have too few in assets with little or no stock market correlation, like utilities and commodities; and are over-exposed to big companies.
John Spiers, Bestinvest managing director, noted: "A balanced portfolio is key if investors are to stand a good chance of achieving their longer-term investment goals."
He added: "Too many investors ignore the split between small, medium and larger sized companies in their portfolios and do not consider hedging with assets that are normally unaffected by stock market movements, for example commodities and natural resources.
"Missing out on such areas can prove costly."
Mr Spiers pointed out that while the FTSE 100 has lost 17 per cent of its value over the last three years the HSBC Global Mining Index has risen 34 per cent.