Investor confidence has fallen sharply since the start of the year, according to JP Morgan Fleming's monthly index.
The survey, which was carried out among a randomly selected national sample of around 500 private investors in early April, shows a fall in confidence for the third consecutive month.
The index stood at 73 in April, down from 92 in January (base index 100 in April 2000).
Yet more investors believe the stockmarket will be higher in six months than those who think it will be lower.
Thirty-seven per cent said they thought the FTSE 100 would be higher in six months time – down from 44 per cent in January – while 21 per cent thought it would be lower.
However, 42 per cent of investors were found to be neutral about future prospects for equities, saying that markets were likely to remain at or around current levels.
JPMF says the dampening of investor sentiment since the start of the year could be due to the prospect of more interest rate rises.
Head of market research Peter Brewster says: “With the FTSE 100 index of leading shares reaching its highest level for nearly two years in April, some investors are starting to question whether there are likely to be further gains in the short term.
“We have already seen markets recover by over a third since July 2002 and now nearly half of investors polled believe there will be little change in the index six months down the line.”