Since ISAs were launched 21 years ago, 4.4 million people have used these savings to help them buy a property.

The average value of ISA savings put towards buying a house was £19,751 – totalling more than £87bn.

However, once parents’ ISA savings were factored in (helping children get on the property ladder) the sum rises to nearly £120bn.

The analysis conducted by the Centre for Economics and Business Research (CEBR) for Scottish Friendly revealed that this figure is greater than the £106bn total value of Northern Ireland’s entire housing stock.

First-time buyers have benefited from ISAs the most with three quarters (73%) saying the savings were used to buy their first home.

However, figures reveal a decline in ISA accounts with the number of adults with either a cash or a stocks and shares ISA falling by nearly one million to 21.2 million between the 2015/16 financial year and 2016/17.

At the same time, the number of individuals with a stocks and shares ISA increased by more than 770,000 to 3.3 million.

One possible reason, according to Scottish Friendly, is that it takes cash savers significantly longer to reach their savings goal than those using a stocks and shares ISA.

Analysis conducted by the CEBR revealed a cash ISA holder who had used their full ISA allowance each year from 1999 to present would have generated a total of £23,245 of tax-free interest.

In contrast, a saver who instead opted to invest their money in the FTSE All-Share Index through a stocks and shares ISA with average annual charges of 1.4% would have accrued a total of £98,934 – more than four times the amount of a cash ISA saver.

Kevin Brown, savings specialist at Scottish Friendly, said: “ISAs have given millions of people, particularly first-time buyers, the opportunity to realise their dream of buying a home.

“During the past 21 years, savers have accrued billions of pounds in ISAs that have been used towards house purchases and many other goals, such as holidays, weddings, home improvements and early-retirement.

“As the ISA now enters its ‘adult years’, our analysis also shows that over the past 21 years, stocks and shares ISAs have on average provided greater returns than secure cash ISAs.

“If you are saving for a long-term goal, such as a house deposit or retirement, then you may want to look beyond just cash accounts as stocks and shares could potentially help you to achieve your target sooner.

“Of course, history doesn’t provide us with certainty to make future decisions and you must remember that the value of investments can go down as well as up and you could get back less than you paid in.”