The number of ISAs sold has more than doubled since the Government raised the tax-free savings allowance, according to new figures.
The amount of money people invested in equity ISAs hit a record level in October 2009, when the annual limit for the amount the over-50s can save in the accounts was increased from £7,200 to £10,200.
The Investment Management Association (IMA) also revealed that there was a further spike in the amounts invested in ISAs in April 2010, when the higher limit for younger age groups was introduced.
Net investments into equity ISAs, once people cashing in or moving their investment were removed from the equation, reached £388 million in October 2009 - the highest level for the month since the accounts were first launched in 1999.
The IMA said £1.16 billion was invested in ISAs during April - the highest monthly total for nine years.
Since last October, total ISA sales have averaged more than £400 million a month, more than double the level during the same period 12 months earlier.
ISAs are tax-free savings accounts into which people can invest up to £10,200 a year.
This can either all be invested into an equity ISA, or £5,100 can be invested in a cash ISA, with the balance paid into an equity one.