Bradford-based Morrisons has benefited from a 30 per cent jump in online sales in London and the South as Southerners get a taste for Morrisons' bargains.
The stand out performer was confectionery, where Morrisons saw a 22 per cent increase in sales as consumers stock up on Halloween and Christmas treats.
Fraser McKevitt, head of retail and consumer insight at Kantar Worldpanel, said: "Low prices have really helped. We are just moving into that time of year when confectionery sales ramp up with Halloween and Christmas. Christmas starts early and people want to stock up. They might succumb to temptation and buy again."
Mr Fraser said that Morrisons is doing well across the board. It was boosted by strong sales of cakes, pastries and fruit, which all saw a 10 per cent leap in sales.
"Ambient grocery, fresh, chilled, frozen and healthcare are all showing strong growth," he said.
"Morrisons' online sales are growing from a very small base. Southern sales are not nearly as strong as they are in Morrisons' heartlands, but they are catching up."
Leeds-based Asda's sales were boosted by strong demand for its value-focused Farm Stores line and its premium Extra Special range.
"Asda is putting effort into Farm Stores," said Mr McKevitt.
"Asda's value own label is up to 88 per cent as people switch out of standard own label to Farm Stores. The premium range is up 22 per cent."
All the big four supermarkets increased sales in the 12 weeks to October 8, although they all lost customer share to Aldi and Lidl, which have both embarked on ambitious store opening programmes.
Aldi and Lidl accounted for half of the entire market's overall growth.
Morrisons was the best performer of the big four, with sales up 2.8 per cent, followed by market leader Tesco's sales increase of 2.1 per cent.
Sainsbury's sales rose 1.9 per cent and Asda saw growth of 1.8 per cent. Aldi and Lidl continued to outperform their major competition with sales up 13.4 per cent and 16 per cent respectively.
Kantar Worldpanel said Christmas has come early for shoppers as they snapped up £69m of chocolate confectionery boxes, £4m of mince pies and £1.1m of Christmas puddings over the past four weeks.
Supermarket sales overall rose 3.1 per cent on the same period last year, the seventeenth period of growth in a row for Britain's grocers.
Like-for-like grocery inflation remained at 3.2 per cent but it is expected to fall below 2 per cent next year.
"The big question is the Brexit negotiations," said Mr McKevitt.
"Will there be extra supply costs in terms of customs? Things are looking better in the short term, but the long term is uncertain."
Kantar Worldpanel said recent stories about the poultry supply chain have not materially dented chicken sales. Fresh poultry sales remained flat in September, while chilled processed poultry increased in value by 6 per cent.
Waitrose sales increased by 2.3 per cent and the upmarket chain has again pulled ahead of Lidl in terms of market share. Waitrose is traditionally stronger in the latter stages of the year as consumers start trading up for the Christmas period.
Co-op's sales fell back by 2.5 per cent. Iceland’s sales grew by 2.6 per cent and Kantar Worldpanel said it is the only bricks and mortar retailer other than Aldi and Lidl not to lose market share over the three month period.