A third of all cash spent on non-food products in November was transacted online as Black Friday “cemented” its position as “an increasingly digital event”.

Online penetration increased to an “all-time high” of 33.8% during the four weeks to November 24, according to the latest BRC-KPMG Retail Sales Monitor.

It marked an increase from 32.6% during the same period last year.

The biggest shift online was seen in non-food. In-store sales of non-food products dropped 1.9% on a total basis and 3.3% in like-for-like terms.

In contrast, online non-food sales grew 2.9% during the month.

Taking all categories into account, like-for-like retail sales dipped 0.5% compared to November 2017.

Total sales advanced 0.5% year on year, although that marked the slowest rate of growth since April, the BRC-KPMG data said.

BRC chief executive Helen Dickinson said: “This month cemented Black Friday as an increasingly digital event, with a record one in every three pounds of non-food purchases made online during the month.

“Black Friday week itself was bigger than last year, but did little to lift the overall pace of spending, with sales growth in November falling to its lowest rate in seven months.

“Weak consumer demand and falling confidence mean that retailers are in for a nerve-wracking run-up to Christmas. Conditions in the industry have been particularly tough since the vote to leave the EU in 2016 and the current uncertainty has only compounded the challenges.”

KPMG retail director Sue Richardson warned that the sales during the Black Friday period won’t necessarily be turned into profits.

“As we’ve come to expect, online sales did fare better but when compared to the previous year’s growth, the performance wasn’t stellar,” she said.

“Sales growth and profitability don’t necessarily go hand-in-hand, especially against a backdrop of deep discounting, so in this environment a laser-like focus on margin and cost base is absolutely essential.”