Britain's millionaire population is set to more than quadruple to 1.7 million people by 2020.
The boom will be fuelled by an estimated 71 per cent rise in the housing market over the next 15 years, less disposable income going on mortgage repayments and growing returns from shares and other investments, the Centre for Economics and Business Research (CEBR) said.
Women will make up 53 per cent of millionaires, boosted by longer lifespan and more generous divorce settlements.
In 2003, about 40 per cent of millionaires were women, a drop of six per cent from the previous year, according to figures from HM Revenue and Customs.
But as richer women tend to hold their wealth in shares, the proportion of women millionaires has grown after the stock market picked up again in 2003.
About 52 per cent of those in the £500,000 to £1 million bracket in 2003 were women.
Future millionaires are also likely to hold much more of their wealth in property. In 2003, millionaires invested an average of 30 per cent of their wealth in property. But those worth between £500,000 and £1 million held 45 per cent of their wealth in the housing market.
The average mortgage payment will also account for around ten per cent less of the average household's disposable income by 2020.
But the number of future millionaires has been revised down from 1.9 million the CEBR predicted two years ago as house price forecasts show signs of slower-than-expected growth.
At present, there are 376,000 millionaires in Britain and numbers are expected to grow to 690,00 by 2010 - but their average age is expected to stay at 56.