A poll of more than 1,000 shoppers for BBC Radio 4 suggests the Black Friday sales are now more popular than the traditional post-Christmas spending spree.
The majority of shoppers (56%) who took part in the survey think Boxing Day sales have lost their appeal.
The British Retail Consortium said they do not see any trend of a reduction in importance of the Boxing Day sales.
The survey, carried out for Radio 4's You and Yours by consumer analysts Savvy Marketing, found 37% expect to spend less this Boxing Day as a result of their spending on Black Friday.
Catherine Shuttleworth, from Savvy Marketing, said: "The data shows that people spent more money this Black Friday than last year and people can't spend that money twice so the Boxing Day sales will suffer.
"Shoppers expect things to be discounted because times are tough and family spending isn't as flexible as it has been."
But a separate survey by Barclaycard says that one in three Britons (34%) will go to the festive sales, up from 23% last year.
Consumer appetite for the post-Christmas sales period fell away last year after an extended period of discounting that began well before November's Black Friday.
VoucherCodes and the Centre for Retail Research also predict the Boxing Day sales will attract more than a third of the UK's population, expecting them to spend a record £4.3 billion - a 12% rise on 2016.
Barclaycard's poll found months of "feeling the squeeze" this year is resulting in many consumers looking forward to the sales to ease their budgets.
Paul Lockstone, managing director at Barclaycard, said: "Last year, Black Friday overshadowed Boxing Day sales as many retailers struggled to maintain consumer interest in what has become a month-long discounting event.
"This year, however, value-seeking consumers appear to be more eager to buy cut-price items across both sales periods as they try to combat rising prices."
Christine Macdonald, marketing manager for intu Braehead in Renfrewshire said: "We expect our Boxing Day sales this year to be as popular as turkey and all the trimmings at the Christmas dinner table.
"If previous years are anything to go by, the early birds out to bag the best of the bargains will be queuing up hours before we are officially due to open the centre at 8am.
"However, stores like Next will start trading even earlier at 6am and we're likely to see the first cars arriving anytime between 4am and 5am.
"No doubt when the rest of the shops open we'll be very busy right up to closing at 7pm."