The Diamond Jubilee has given retailers a much-needed shot in the arm, with sales soaring by more than 12% compared to the equivalent period last year.

New figures from Nielsen showed grocery sales up 12.5% in the week leading to the celebrations. Sales of crisps and snacks were up 10%, with confectionery up 9% and growth of 7% for soft drinks and for alcohol.

But the dismal weather throughout much of May meant sales for the month as a whole were up just 3.3% – in line with much of 2012. Volumes were down 0.9% over the month.

“Overall, May was a month of better momentum across food retailing, with the major supermarkets issuing a deluge of cash savings and discounts, actively encouraging shoppers to visit and spend,” said Nielsen’s Mike Watkins.

“This has been a familiar pattern over the past six months. Promotional spend remains at 35% of overall basket sales at the grocery multiples and we anticipate these trends continuing for the next three months.”

Nielsen’s data showing Asda emerging as a major winner in the 12 weeks to 26 May, with sales up 6.3% on the same period last year and its market share climbing to 16.3%.

Morrisons posted growth of just 0.6% compared to last year and saw its share of the market slip from 11.4% to 11.2%.