Consumers are paying £100 more a year for their groceries

Market researcher Kantar Worldpanel said inflation was driven by sharp increases in the price of butter, fish and fresh pork. Only a few products, such as fresh poultry and crisps, are seeing a fall in price.

​Fraser McKevitt, head of retail and consumer insight at Kantar Worldpanel, said inflation has added over £100 to consumers' annual grocery bill.

"That's pretty tough," he said.

"People are looking for ways to trim spending. Own label products are growing a lot more quickly than branded."

They are also visiting discounters Aldi and Lidl more frequently.

​Aldi was Britain's fastest growing grocer during the latest quarter, with sales up 15.1 per cent year on year.

"Aldi are winning a lot of awards," said Mr McKevitt.

"They are saying: our food is cheap but it's good quality. They also have a big emphasis on British meat."

Aldi's UK CEO ​Matthew Barnes said:​ ​“After attracting more than a million new customers in 2017, we are delighted to end the year as the UK’s fastest-growing supermarket.

“We are confident this will be our best-ever Christmas, as our festive selection comprises more than 400 products - including 160 new lines - of outstanding quality, such as our Specially Selected Exquisite Vintage Pudding, which recently won the Christmas Gold Q at the Quality Food Awards.

“The key difference is that we sell these products at unrivalled prices, meaning our customers can enjoy indulgent Christmas treats like our Prosecco Magnum or Fresh British Sirloin of Beef with Porcini, without having to pay over the odds for them.”

Market leader Tesco was the best performing of Britain’s big four supermarkets over the 12 week period. Its sales rose 2.5 per cent, ahead of growth of 2.0 per cent at number two player Sainsbury's.

Bradford-based Morrisons saw growth of 1.4 per cent while Leeds-based Asda's sales rose 1.2 per cent.

"Growth remains in the slow lane at Asda, but they are growing," said Mr McKevitt.

"Asda's premium own label is growing at 15 per cent. At the other end Farm Stores is doing well."

He said there was not a lot to separate Tesco, Sainsbury's, Asda and Morrisons.

Despite the higher costs, shoppers are expected to splash out on the Friday and Saturday before Christmas - December 22 and 23 - and part with £1.5bn.

"People do tend to splash out at Christmas although the economic mood music isn't great," said Mr McKevitt.

In a sign that people could be drowning their sorrows, alcohol sales are up by nearly £172m compared with this time last year, primarily due to consumers choosing more expensive festive tipples like gin, whisky and sparkling wine.

​"Alcohol sales are a prime example of people willing to spend money. The more expensive lines are doing better," said Mr McKevitt.​

​"Despite higher prices, the British public is well into the swing of festive shopping.

"Christmas Day falls on a Monday this year. Last time that happened, in 2006, the Friday before was the most popular day for grocery shopping that year.

"If we see a similar pattern in 2017, Friday 22 December is likely to win out as the grocers enjoy not only the biggest shopping day of 2017, but the most successful ever recorded."