The number of people out shopping in the UK in November dropped to its lowest level since the 2008 recession, retail researchers say.
Footfall at shopping centres, retail parks and High Streets fell 3.2%, according to analysis firm Springboard.
The figures showed the Black Friday effect was driving more shopping online during a longer period, the firm said.
The decline was "indisputable evidence" that Black Friday was of no benefit to physical stores, it added.
Springboard said it expected footfall to decline by 4.2% year-on-year in December, a bigger drop than the 3.5% decrease seen in December 2017.
"These figures are the worst footfall figures that Springboard has recorded since the recession and we're not actually in recession," said Diane Wehrle, Springboard's marketing and insights director.
"It's clear that something significant is happening out there in consumer demand. It has really railed back this year."
Ms Wehrle warned that more High Street chains could collapse in January.
The growth of online shopping has been one of the main challenges facing the UK's High Streets, which have seen a number of store chains collapse this year as trading conditions worsen.
Springboard said the UK's political turmoil over Brexit was also having an impact on shoppers' purchasing decisions.
"As we head into the zenith of the retail trading calendar, both retailers and consumers alike are in the midst of the greatest degree of uncertainty in recent times," said Ms Wehrle.
"However, the fact that the Parliamentary vote is not taking place until the middle of December might deliver a slight glimmer of hope for some large-ticket item retailers, as consumers may purchase now rather than later, in an attempt to outrun inflationary pressures that are expected should the Brexit deal not be ratified."