RBS has advised clients to brace for a “cataclysmic year” and a global deflationary crisis, warning that major stock markets could fall by a fifth and oil may plummet to $16 a barrel.

The bank’s credit team said markets are flashing stress alerts akin to the turbulent months before the Lehman crisis in 2008. “Sell everything except high quality bonds. This is about return of capital, not return on capital. In a crowded hall, exit doors are small,” it said in a client note.

Andrew Roberts, the bank’s research chief for European economics and rates, said that global trade and loans are contracting, a nasty cocktail for corporate balance sheets and equity earnings. This is particularly ominous given that global debt ratios have reached record highs.

“China has set off a major correction and it is going to snowball. Equities and credit have become very dangerous, and we have hardly even begun to retrace the 'Goldlocks love-in' of the last two years,” he said.

Mr Roberts expects Wall Street and European stocks to fall by 10pc to 20pc, with even an deeper slide for the FTSE 100 given its high weighting of energy and commodities companies. “London is vulnerable to a negative shock. All these people who are ‘long’ oil and mining companies thinking that the dividends are safe are going to discover that they’re not at all safe,” he said.