Simon Roberts, the chief executive of Sainsbury’s, earlier this month warned that uncertainty surrounding the Budget was deterring shoppers from spending.

His comments followed underwhelming first quarter results in July, with sales of clothing and non-food items declining as a result of poor summer weather. Sainsbury’s is scheduled to present half-year results in early November.

Some analysts argued that Qatar Investment Authority’s decision to dump stock was not related to upcoming events.

Analysts at JP Morgan Cazenove said: “Given the strategic nature of the shareholder, we do not see [the share disposal] being necessarily linked to upcoming events.”

Regardless, the sale comes against a backdrop of frenzied activity in the stock market as investors scramble to adjust their finances ahead of the Budget.

Executives at Britain’s biggest companies have sold more than £1bn of shares since the election was called.

Meanwhile, investors offloaded £666m of UK shares in September amid fears that Ms Reeves could increase the rate of capital gains tax, a levy paid on any profits from selling shares or any investment.

The Government was on Thursday forced to deny reports that the Treasury was planning to raise capital gains tax to 39pc.

Capital gains tax is a levy charged on investment profits, though it is only payable by individuals rather than companies such as the QIA.