Damian McBride appeared to suggest that the stock market dip could lead to civil disorder or other situations where it would be unreasonable for someone to leave the house.

"Advice on the looming crash, No.1: get hard cash in a safe place now; don't assume banks & cashpoints will be open, or bank cards will work," he tweeted.

"Crash advice No.2: do you have enough bottled water, tinned goods & other essentials at home to live a month indoors? If not, get shopping.

"Crash advice No.3: agree a rally point with your loved ones in case transport and communication gets cut off; somewhere you can all head to."

Mr McBride credited his former boss Gordon Brown with preventing a cataclysm by nationalising the banking system during the 2008 crash.