The survey ran from 28 June to 11 July, capturing business sentiment in the immediate aftermath of the Brexit decision and during a period of significant political uncertainty. It found significant downturns in corporate optimism and risk appetite, with CFOs shifting to defensive balance sheet strategies and becoming more cautious of all forms of spending.

Getting on for three quarters (73%) of CFOs said that they were less optimistic about the financial prospects for their company, well over double the 32% reported in Q1, and higher than during the fallout from the Lehman collapse in 2008.

Despite the gloomy prognosis of the survey, investment in UK companies was buoyed today by the announcement that Japan’s SoftBank is to acquire ARM Holdings, the UK chip designer which powers the processors in everything from iPhones to laptops in a £24bn acquisition. It has also pledged to create up to 2,000 additional jobs at the Cambridge-based IT innovator.

Almost all (95%) of CFOs reported the level of uncertainty facing their business is above normal, high or very high, up from 83% in Q1 and returning to levels last seen in the Euro crisis in 2012.

Just 8% of CFOs say now is a good time to take risk onto their balance sheet, down from 25% in the last quarter and the lowest level since Q1 2009.

There has been a sharp rise in CFOs (63%) who say they expect revenues at their firms to decrease in the next year, up from 11% in Q1 and the highest level recorded. However, 23% predict an increase in revenues. In addition, 70% expect operating margins to decrease, the highest level on record, and up from 37% in Q1.

The majority (82%) of CFOs expect their firms to shrink capital spending in the next year, with 83% forecasting a slowdown in hiring. Both are the highest level recorded by Deloitte’s survey and up significantly from 34% and 29%, respectively, in Q1.

The proportion forecasting a cut in discretionary spending (82%) is the highest since Q4 2011.

Asked about the impact of Brexit on their spending plans over the next three years, half of CFOs (58%) expected capital spending to be somewhat or significantly lower over this period, 66% expected hiring to be lower and 74% saw discretionary spending being lower.

Overall, 68% of CFOs believe that leaving the EU will lead to a deterioration in the UK business environment in the long term, while 20% expect little change and 13% expect an improvement.

Deloitte says that for the first time since Q1 2015, the top two balance sheet priorities for major UK corporates are defensive, with 47% of CFOs citing the need to reduce costs and 41% looking to increase cashflow.

Asked about the steps the government should take to support economic activity, 91% of CFOs said that a strong signal about the government’s aims in the negotiations with the EU should be a priority while 88% said that maintaining the solvency and liquidity of the banking system was essential.

In third place, 25% said that the government should continue with a deficit reduction plan while 16% said that raising public expenditure would help. Just 9% say that tax cuts would help economic activity, 6% call for additional quantitative easing and 3% favour cuts to interest rates.

David Sproul, senior partner and chief executive of Deloitte, said: ‘The outcome of the EU referendum has triggered a sharp, negative response from the corporate sector.

‘The faster-than-expected appointment of a new prime minister removes one source of uncertainty, now the government must set out its vision for the UK’s future relationship with the EU to provide further stability and reassurance. As companies begin to feel the environment stabilising, we may see confidence improve in next quarter’s survey.

Separately, research from Begbies Traynor suggests UK property and construction sectors are likely to bear the brunt of Brexit, with nearly 50,000 firms at risk.

According to the firm's Red Flag Alert research for Q2 2016, which monitors the financial health of UK companies, in the three months preceding the EU referendum, levels of ‘significant’ financial distress among UK businesses fell for the first time since Q3 2015.

There was a 4% drop compared to Q2 2016, from 274,595 struggling businesses in Q1 2016 down to 263,517 companies in the past three months, of which 93% (244,402) were small to medium sized businesses (SMEs).

The sector most exposed to economic volatility remains to be UK construction and real estate, in which 49,186 firms were classified as experiencing ‘significant’ financial distress in the period.

Overall, levels of financial distress decreased across every sector and every region of the UK economy, but the most marked improvement in financial health during Q2 was among London-based businesses, where the number of companies experiencing ‘significant’ distress fell by 5% to 43,737 (Q1 2016: 46,234 companies).

Julie Palmer, partner at Begbies Traynor, said: ‘UK construction and real estate has certainly been hit hardest following the Brexit result, with many high profile investors pulling out of UK property over the past three weeks. With experts predicting that London property prices could plummet by as much as 20% and nearly 50,000 firms in this sector already suffering from “significant” financial distress, the foundations for this sector are looking decidedly shaky.’