Shoppers are expected to spend more than £4bn in the Boxing Day sales on Thursday, but the annual discount extravaganza is likely to be dampened after a month of price cuts.

Sales in stores are expected to be down by just over 12% to £3.2bn, according to VoucherCodes and the Centre for Retail Research, while bank holiday queues are expected to be up to 2% shorter than they used to be as the post-Christmas sales have been eclipsed by November’s Black Friday promotional stint.

“Boxing Day has been slipping down the hierarchy of shopping days for a number of years,” said Diane Wehrle, an insight director at the shopper monitoring firm Springboard. “Last year the volume of shoppers was 30% bigger on Black Friday.”

She said the rise of more complex families, with ex-partners and more in-laws to visit, meant more people used the bank holiday to visit relatives, with 27 and 28 December now much busier shopping days.

Four consecutive years of decline in shopper numbers mean there will be at least 11% fewer people visiting high streets, shopping centres and retail parks than on Boxing Day 2015.

Richard Lim, the chief executive of the consultancy Retail Economics, said Black Friday sucked forward spending, making things tougher for retailers at the end of the year.

“An element of discount fatigue creeps into consumers’ mindsets by the time Boxing Day sales come about,” he said. “Perhaps the one exception is around furniture and flooring, where consumers wait for the highly anticipated sales period for big-ticket purchases.”

Discounting has been particularly heavy this November and December as retailers have tried to tempt out shoppers who were reluctant to spend given the uncertainty around Brexit and the 12 December general election. Relatively warm and wet weather has also hit clothing sales with the number of shoppers out and about on Christmas Eve down by about 8% compared to 2018.

Clearance sales before the planned closure of more than 20 Debenhams stores in January, and troubles at chains including House of Fraser, Bonmarché and Mothercare, have made it easy to find a bargain.

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While many still enjoy an excuse to get out of the house after a day of relatives and too much food, the rise of online shopping has also hit the Boxing Day sales. Official figures out last week showed that nearly a fifth of all retail sales were made online. The Centre for Retail Research is predicting £1.1bn will be spent online on Boxing Day this year, up more than 10% on 2018.

What is more, many retailers such as John Lewis and Marks & Spencer begin offering discounts online on Christmas Eve, leading to a rise in shopping on Christmas Day itself, which lessens the draw of Boxing Day price cuts in stores. More than £1bn is likely to be spent digitally on Christmas Day according to the Centre for Retail Research.

IMRG, the online retailers’ body, said Christmas Day was not only about picking up bargains using vouchers and cash received as a gift. “Gifting companies say there is a massive spike in buying an experience, like a hotel break or driving a car, on Christmas morning as people forget to buy a present for people and those gifts are instant.”

But for some, Boxing Day remains an opportunity to treat themselves after the hectic buildup is over. “It is like an oasis after the mayhem and pressure of buying presents for other people,” said Wehrle. “You can go shopping for a few hours and have something to eat or go to the cinema. I think it’s less about standing in a queue waiting for a department store to open so you can grab a bargain.”

While many retailers have been offering discounts for months, household names such as Next, John Lewis, Harrods and Selfridges tend to hold back until Boxing Day or the 27th, creating events that can still draw a crowd.

The property firm Intu said it expected more than 1 million people to flock to its shopping centres, which include Lakeside in Essex and the Metrocentre in Gateshead, on Boxing Day.

Its commercial director, Trevor Pereira, said: “We expect it to be one of our busiest shopping days of the year. Going shopping on Boxing Day is a yearly tradition for many and people come to our centres to enjoy a great experience that cannot be matched online.”