Analysis by the Centre for Economics and Business Research on behalf of Scottish Friendly found the number of female ISA subscribers fell by 114% between 2015-16 and 2016-17, the largest annual decrease since records began in 1999.

Women still account for the majority of all ISA subscribers (52%) but there were nearly three-quarter of a million (786,000) fewer female subscribers in 2016-17 compared to the previous financial year.

In 2011-12, women accounted for the majority of ISA subscriptions for the first time and the number continued to rise until 2015-16 where it has since plateaued.

But Ms Mackay believes this recent drop in numbers is a warning to the industry that more needs to be done to ensure women continue to take advantage of tax-efficient savings.

She said: “Women are more likely to be financially disadvantaged by career breaks to raise a family or to care for relatives. Until now, the growth in ISA demand among women could perhaps be attributed to rising employment and higher incomes for women.

“Sadly, it appears we have now reached a tipping point and it’s important the industry closely monitors this situation to ensure the number of women taking advantage of tax-efficient savings doesn’t fall away.”

Although ISAs generally are equally subscribed by men and women, stocks and shares ISAs are heavily favoured by older age groups and are also more popular among men. The latter accounted for 57% of all stocks and shares ISA subscriptions in 2016-17.

Among women who did subscribe to a stocks and shares ISA in 2016-17, only 4% are aged between 25 and 34 and a further 13% between 35 and 44.

By contrast, there were 73,000 men aged between 25 and 34 that subscribed to a stocks and shares ISAs in 2016-17. This is more than double the corresponding figure for women of the same age (36,000).

Ms Mackay added: “The under-representation of female investors needs to change, especially in an environment where women’s long-term savings typically fall well behind men’s over a lifetime. For small amounts, for example, £10 a month, women can start investing into a stocks and shares ISA, and the key is to try and start doing so as early as possible.”  

She provided the following tips for first-time female investors:

• Try and get started as soon as you can, even if you only have small amounts to invest. A little and often approach to investing can soon add up.
• Many people are unaware that you can have more than one type of ISA so don’t overlook investing because you already have a cash ISA
• The ‘stepping stone’ approach could be used as and when you have more disposable income. For example, start from £10 a month and if you can, increase it by what you can afford every year
• If you have a Junior ISA for your children, once it’s open anyone can contribute so why not ask the family to get involved. Grandparents may have more disposable income to invest towards their grandchildren’s future