More than two fifths of regular ISA savers would increase their investments if they knew how to source financial advice - which almost a quarter (23%) admitted they didn't, according to MetLife.
The provider's nationwide study found almost half (45%) of ISA savers thought the current rules and options for stocks and shares ISAs were too complex for them to understand, highlighting the need for independent advice.
A mere fifth of those questioned held equity ISAs and more than a third said they would not invest in them because of fears about volatility.
MetLife questioned 1,071 employed adults aged 18 and above during January and February 2017, ahead of the increase of the tax-free ISA contribution limit to £20,000 from £15,240.
It found about one in five (18%) had sought advice on their ISA savings at some stage, while more than a third (38%) would value advice offered at work.
MetLife wealth management director Simon Massey said: "The increased ISA contribution limit to £20,000 dramatically increases the attraction of ISAs as a tax-free savings option but turns the spotlight on the need for advice.
"Savers should be getting independent face-to-face advice if they are investing such large sums and the concern is that the current rules and options are too complex."
He added: "There is a real need for increased savings choice particularly when interest rates are at historic lows and there is a clear need for advice on maximising investment opportunities."
Last August, the financial ombudsman service reported misselling complaints related to stocks and shares ISAs were up 166% in a year.
In January, research from Aviva found consumers were so unfamiliar with financial terminology they were more likely to know the capital of Peru than the correct definition of a defined benefit pension.
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