The figures represented a slight improvement on August 2022, where there was a 4.1% fall from the same period the year before, but September underperformed compared with September 2021, which saw a 6.8% rise year on year.

The retail index is based on tracked online sales for more than 200 retailers and has been run since 2000 by retail industry body Interactive Media in Retail Group (IMRG) and technology firm Capgemini.

The index said that September was a “complicated month” for online retail, owing to the 10 days of national mourning following the dead of Queen Elizabeth II, the announcement of the energy cap freeze and the government’s ‘mini budget’ that stoked a financial and political crisis.

Clothing was the only retail category to see positive growth in September, rising from +2.8% in August to +4.3%, although menswear struggled at a 3% fall, albeit up from -7.1% in August.

Electricals was down 8.2%, although only 0.7 percentage points lower than August, and gifts fell 9.3%.

The heaviest declines in September were for beer, wines and spirits (-27.3%) and garden (-19.3%).

Andy Mulcahy, strategy and insight director at IMRG, said: “September featured such economic turbulence that it’s very difficult to understand whether shopper confidence has risen, fallen or stayed the same.

“However, one definite positive was a spike in online spend toward the end of the month when retailers promote their ‘100 days till Christmas’ campaigns. The spend was 17% higher in week four – the second highest rate of the past four years for that period.

“That at least suggests customer interest and responsiveness; we can’t know how the turbulence will unfold over the next few key months for retailers, but if that spike had not occurred this year, it would have been very concerning.”

Simon Binge, commerce senior manager, customer transformation at Capgemini, said: “Despite an eventful month of disruption for UK shoppers, the online retail market performed largely in line with the previous four months, with an average -3.3% year-on-year sales decline for July to September.

“Whether the premium sector can entice shoppers back during the next few months of expected promotional activity or the mid-market sector continues to win the battle for the wallet remains to be seen.”