The study shows 32 per cent are unsure about whether they would use the full allowance, with some waiting to see what their financial position is before committing their money.
A further 24 per cent say they do not plan to make further investments.
The new increase in the Isa allowance from £7,200 to £10,200 will be open to over 50s from October 6 of this year, while other investors will have to wait until April of next year before the allowance applies to them.
L&G found 53 per cent of regular investors who invest at least once a year were aware of the forthcoming Isa changes.
Legal & General savings marketing director Claire Evans says: “It is reassuring that only a quarter of active savers say they are not planning to invest. Investors recognise the valuable tax savings they are being offered and the majority are likely to use their allowance before the end of the tax year.”
“It makes sense for the over 50s to take advantage of the increase in Isa allowances if they have any savings in deposit accounts, which do not offer the same generous tax incentives.”