The Brexit vote has shaken stock markets, shocked businesses and sent sterling plunging. Mark Carney, governor of the Bank of England, said last week: "The economic outlook has deteriorated and monetary policy easing will likely be required over the summer."
Consumer confidence is also at its lowest level since May 2013, according to a YouGov poll that surveys people on job security, business activity, house values and household finances.
There is already talk of advertisers putting their media spend on hold. Sectors such as house-builders, airlines and financial services are likely to cut spend, while easyJet and Foxtons have issued profit warnings.
The fear is that expenditure on advertising is easy to cut, even though there is considerable case-study evidence to show that brands that keep investing during a downturn perform better financially.
VCCP Partnership has already started budgeting for a 5% decline in fees and Adam & Eve/DDB has said a US client pulled a £1.5m-fee project on the day after the referendum result.
But, with the woes of the 2008-09 slump still fresh in people’s memories, industry leaders are anxious not to talk themselves into a slowdown.
Mike Dodds, chief executive of Proximity London, says: "While all this instability can be unnerving for brands, it can also represent a huge opportunity.
"In previous economic downturns, I’ve seen challenger brands turning the situation to their advantage by increasing their spend – as opposed to cutting it – and stealing market share from their more cautious competitors."
Richard Exon, co-founder of Joint, says: "Lack of political leadership has created today’s toxic uncertainty. Bankers and senior marketers, however, have the authority to shape the economy we all operate in. If banks keep lending and brands keep spending, people will keep shopping."
Dixons Carphone is among the brands to see "opportunities for additional growth" after Brexit.
Ian Whittaker, analyst at investment bank Liberum, believes there is little evidence to show that economic confidence has been seriously dented. He argues that advertisers can sometimes shoot themselves in the foot by thinking consumers aren’t spending.
Still, turkeys don’t vote for Christmas, so few media agencies and media owners are likely to recommend brands cut their spend. It remains to be seen what the state of the UK ad market will be by December.