Measuring post-Brexit sentiment, the Index has fallen eight points to -9 with every key measure used to calculated the Index falling. There has not been a sharper drop in this long-running survey for 21 years (December 1994 ).

Splitting the Core Index result by how people said they voted in the referendum, Remainers were at -13 with Leavers more optimistic at -5. The survey among 2002 online respondents was run from June 30^th to July 5^th to capture the post-Brexit mood of consumers.

Demographic differences show that confidence has dropped more dramatically in the North than the South ( 19 point drop compared to a 2 point drop respectively).

The results found that six in 10 ( 60%) expect the general economic situation to get worse in the next 12 months, up from 46% in June. Only 20% of consumers expect it to improve, down from 27% in June. The proportion of people who believe prices will increase rapidly in the next 12 months has jumped 20 percentage points from 13% to 33%.

Joe Staton, head of market dynamics at GfK, said: "Our analysis suggests that in the immediate aftermath of the referendum, sectors like travel, fashion and lifestyle, home, living, DIY and grocery are particularly vulnerable to consumers cutting back their discretionary spending.

"As we’ve learnt from previous periods of uncertainty, consumers turn to well-known brands they love and trust as a guarantee of quality and value for money. Now is the time for companies to understand and respond to consumer concerns by anticipating and meeting their needs.”