New research by Halifax, based on data from the Inland Revenue, shows that cash continues to be the most popular ISA category, recording growth in balances of 129% over three years to March 2004 to £81.6bn. Stocks and shares ISAs saw growth of 68% over the past three years.

Over 9 million Individual Savings Accounts (ISAs) were opened UK-wide in the first half of 2004/05, up 6% on the same period last year. UK savers held £126bn in ISAs in 2003/04 with £81.6bn invested in cash ISAs, compared with £44.2bn in stocks and shares ISAs.

Key points:

Cash ISAs continue to be the most popular. A total of £126 billion was held in ISA accounts last year, with £81.6 billion held in cash ISAs. This compares with £44.2 billion in stocks and shares ISAs and just £522 million in insurance ISAs.

Savers in the South West of England are most likely to have an ISA, with 26% of individuals aged 16+ subscribing in 2001/02, the latest regional data available. The South West is followed by the South East at 25%. Northern Ireland has the UK's lowest proportion of ISA savers (16%), followed by London (21%) and Wales and the North East at 22% each.

The largest increase in ISA subscribers has been in Scotland, with subscriptions rising by 23% over the two years to March 2002. The smallest increase was in Nortern Ireland with only a 2.5% increase seen.

The most ISA accounts are in the South East of England (1,618,000). The least are in Northern Ireland (204,000) and the North East (457,000).

Every region of the UK has saw an increase in the number of people saving in ISAs between 2000 and 2002, with Scotland experiencing the fastest growth in of 22.7%. Growth was slowest in Northern Ireland, where the number of people with an ISA rose by just 2.5%.

58% of all ISA holders have less than £6000 in their ISA accounts. In the North East 64% have less than £6000 in their ISA account, the most of any region. In London savers tend to have larger balances and 46% of London ISA holders have more than £6000 in their acccount.

Cheryl Millington, head of savings at Halifax, said: "Less than a quarter of the UK adult population subscribe to an ISA each year, despite the fact they are one of the most tax effective ways of saving for the future. We hope that a recent Government consultation on extending the current ISA limits will encourage more people to benefit from tax-free savings."

"Perhaps because most people are comfortable with the concept of cash deposits, cash ISAs are the most popular choice and more than two-thirds of those people with an ISA have chosen to save in the cash version."