The British Retail Consortium (BRC) reported that in London sales jumped 12 per cent in December – the best performance since it started publishing the figures in 2002.
Visitors from Europe, China and the Middle East hit the shops, taking advantage of the weak pound.
The surge in sales compared with a rise of just 4.2 per cent in the rest of Britain.
Director general of the BRC, Stephen Robertson said: “This is a dazzling performance, London’s best December sales growth since this survey began in 2002.
“The result is boosted because the comparison is with terrible figures a year ago but this is outstanding growth by any interpretation.
“Generally customers were a lot more positive than the year before, so more willing and able to spend. A big Saturday Boxing Day start to many post-Christmas sales produced a strong extra day’s trading for lots of retailers and the weak pound tempted overseas shoppers to London.
“Wintry weather kept people away from shops on some days but when they did go they spent more.
“But, given the prospects for jobs, wages and taxes in 2010, don’t assume customers will go on spending like this.”
Food sales were particularly strong, helped by rising prices, and clothes and shoes sold well thanks to the wintry weather. Beauty products and jewellery were also popular.
December sales at John Lewis jumped 19 per cent in Oxford Street and 16 per cent at Peter Jones in Sloane Square.
Sales last week were up nine per cent at John Lewis and 15 per cent at Peter Jones.
Helen Dickinson, head of retail at KPMG, said: “Although the rest of the country saw a slow build-up to Christmas, these are great figures and Christmas provided an opportunity for department stores to outperform.”
Next and John Lewis are among the firms who have reported upbeat figures reflecting the improvement on the high street.