Insights agency Opinium said only 8% of IFAs have seen an increase in their clients paying into ISAs since the rules changed.

The majority of IFAs (87%) said they have not seen any change in behaviour among their clients.

In one of the biggest shake-ups of ISA rules in recent years, and in a bid to encourage competition and boost rates, earlier this year the government allowed savers to pay into more than one of each type of ISA annually.

The changes had been announced as part of the then Chancellor Jeremy Hunt’s Autumn Statement in November.

The new rules allowed multiple subscriptions to ISAs of the same type every year from April. They also opened the door to partial transfers of ISA funds between providers and enabling some fractional shares to become eligible ISA investments.

the Treasury said at the time: "The government is making changes to simplify ISAs and provide more choice.”

In March research showed that Almost 4 in 5 (78%) of savers were in the dark about the rule changes.

Alexa Nightingale, global head of financial services research at Opinium said: “The change in ISA rules came into force in April this year, but appears to have made little impact on savers’ behaviour.

“It was hoped that they would feel empowered to seek out the best returns by allowing them to easily move between different providers.

“With interest rates finally beginning to fall, advisers will likely encourage clients to seek the best returns possible, so we may see more of an uptick in people paying into multiple ISAs as the year goes on.”

• Opinium Research carried out an online survey of 200 financial advisers, between 3–12 July.