Graham Beale said such a move would be particularly helpful for those older savers approaching retirement who have stocks and shares ISAs but want more flexibility about how they manage their capital and access their cash, especially those who prefer to de-risk their capital by putting it into cash savings rather than stocks and shares.

According to research by Nationwide, more than one in ten of the UK’s over 45 population would like to transfer funds back into cash ISAs, which they feel are more secure. Sixty percent of those polled were unaware that they cannot do so without losing the tax-free wrapper.

Beale said: “Certainty of income and protecting capital is hugely important for older savers, particularly where it is a vital part of their retirement income. So, it is no surprise to see our research show that while one in five older savers have a stocks and shares ISA, more than half of them have thought about transferring to a cash ISA.”

Nationwide’s research shows that more than a third of Britons with a cash ISA have used up their full allowance for the 2013/2014 tax year, while only eight percent with a stocks and shares ISA have done so.

Beale concluded: “At present, you can put twice as much money into a stocks and shares ISA than you can into a cash ISA, which clearly means people with stocks and shares ISAs have the potential to earn more tax-free interest than their cash ISA saving counterparts. This doesn’t seem fair to me, so in the run up to this week’s budget, I wrote to the Chancellor calling on him to increase the cash ISA limit so it is equal to the higher stocks and shares ISA limit.”