More than £100 billion will be wiped off the personal fortunes of Britain's wealthiest industrialists and entrepreneurs in the coming months as tumbling stock markets and sliding property prices take their toll.

Steel magnates, City brokers, hedge fund managers and the owners of Premier League football clubs will see their spending power cut, and that is likely to influence the price of urban mansions and hit sales of luxury goods.

The grim prognosis for the nation's über-rich comes from Philip Beresford, the wealth expert who compiles the annual Rich List for The Sunday Times.

In April, the collected wealth of the country's top thousand multimillionaires totalled £412.8 billion, according to his calculations. “If current trends continue, we will be lucky to make £300 billion next time around,” Dr Beresford told The Times. “It is too early to be exact, but I estimate that at least one third will be wiped off the personal fortunes of the top 1,000 by next April.”

Dr Beresford added that the entry point for individuals to qualify for the Rich List will roughly halve from £80million this year to £40 million when the List appears next April.

His forecast comes as some of the UK's high-profile billionaires see their personal fortunes dwindling as roiling markets take the shine off the companies they have built, in some cases from scratch.

Lakshmi Mittal, 58, the steel magnate behind ArcelorMittal, has seen more than £20 billion wiped off the value of his individual wealth in the past five months. Mr Mittal and his family topped the Rich List by a long stretch this year with assets estimated at £27.7 billion.

The Mittals own 43 per cent of ArcelorMittal, but tumbling steel prices and a tail-off in the com-modities boom has sparked a fall of nearly two thirds in its share price since May.

Dr Beresford said that it was too early to predict where Mr Mittal and his family would finish the year, but acknowledged him to be the biggest sufferer.

Mike Ashley, the founder of Sports Direct and owner of the Lillywhites retailing superstore in Piccadilly Circus, Central London, has also seen his financial fortunes stumble. Mr Ashley put Newcastle United FC up for sale last month after falling out with its coach, Kevin Keegan, over strategy and amid threats from angry fans watching the team lose.

Mr Ashley, who ploughed millions of his own money into the Magpies, has seen the value of Sports Direct, which he floated for £1.1 billion last year, crumble to less than £170 million today. His tills stopped jingling as England failed to qualify for the European championship and kit sales took a dive.

Many of the super-rich have been casualties of the credit crunch. Joe Lewis, the Bahamas-based trader who owns Tottenham Hotspur, lost an estimated £600 million in his investment in Bear Stearns, the Wall Street securities company whose near-collapse led to its sale in March toJPMorgan Chase.

In the City, Michael Spencer, the founder of Icap, the interdealer broker, has been forced to watch as more than £480 million has been wiped off the value of his personal stake in the firm since the credit crunch took root.

Mr Spencer, who is also treasurer to the Conservative Party, holds about a 20 per cent stake in Icap, which initially profited handsomely from the volatility gripping world markets.

However, as some of Wall Street's banking titans began to collapse, investors started to worry that business would dry up as counter-parties for the broker to stand between dwindled.

Bruno Schroder and his family, the biggest investors in the fund manager Schroders, have also been big losers at the hands of sapping market confidence in financial firms.

“It is the big stock market, quoted people, who will suffer the most, as well as those British millionaires who are heavily into property,” Dr Beresford said. “Ironically, most of the foreign non-doms in the UK will probably get off relatively lightly. Most of their investments are more liquid and relatively easy to transfer out of.”

Most to lose . . .

Sunday Times Rich List 2008

1 Lakshmi Mittal and family, £27bn
2 Roman Abramovich, £11bn
3 The Duke of Westminster, £7bn
4 Sri and Gopi Hinduja, £6.2bn
5 Alisher Usmanov, £5.7bn
6 Ernesto and Kirsty Bertarelli, £5.6bn
7 Hans Rausing and family, £5.4bn
8 John Fredriksen, £4.6bn
9 Sir Philip and Lady Green, £4.3bn
10 David and Simon Reuben, £4.3bn