The number of millionaire households in the UK is predicted to rise by 60% to more than 2.4 million within the next 10 years, a new study has found.

Britain's richest are expected to have a combined wealth of more than £6.9 trillion by 2017, and the number of households with a fortune of £5m is due to increase by 120% to 126,000, the Household Wealth Index revealed.

The study, developed by Barclays Wealth and the Economist Intelligence Unit, forecasts that the current rise in the number of millionaire households - up from 1.5 million last year - will bring the UK the seventh-highest concentration of wealth in the world.

But the experts behind the study said this could leave the UK vulnerable to a shock from an economic downturn.

There was no breakdown available of the number of millionaire households in Scotland. However, recent figures show that Scotland had 12,000 such households.

Recent research showed the number of millionaire households in Scotland was dwarfed by the number in south-east England. One in 10 households in London was worth £1m or more, compared with one in 183 in Scotland.

Michael Dicks, head of research and investment strategy at Barclays Wealth, said of the latest research: "The UK will continue to outperform Europe and remain a significant centre for wealth generation over the next decade.

"We believe that any financial downturn would have a greater short-term impact on wealth creation in the UK than in other European countries, which do not have the concentration of financial services activity seen in London."

America is set to retain its global status as the world's richest nation, the study predicts, although it suggests that emerging markets, such as China and India, will make significant gains by 2017.

The index shows that the top five wealthiest nations by distribution of household wealth will be led by the US, followed by Japan, with China in third place up from seventh last year, the UK in fourth position and Germany in fifth.

India is expected to move up from 14th position in 2007 to eighth place in 2017, while Russia could be catapulted from 19th place to 11th place.

The Household Wealth Index figures come days after a new study showed that plenty of homebuyers were willing to splash out for a million-pound mansion despite the global credit crunch.

Research carried out for the Bank of Scotland showed that the top end of Scotland's housing market surged ahead of the rest of the UK last year with a 138% increase in homes fetching £1m or more.

The study showed that million pound properties still account for a small proportion of property sales - just 0.2% last year. However, the increase in Scotland - 343 sales last year compared to 144 the previous year - was far ahead of the 36% increase in Britain as a whole.

London and the south-east of England accounted for 78% of the total number of million-pound properties sold, while Scotland accounted for 4%.