Investors are bracing themselves for a hefty fall in financial markets this week after growing concerns that Britain could vote to leave the European Union sent the pound tumbling and stocks in Asia plummeting this morning.

The pound fell to an eight-week low against the dollar and a three-year low against the yen as jittery investors shifted into safer assets.

The flight to lower-yielding investments came as Asian stock markets plunged, with dealers awaiting key meetings this week of the US and Japanese central banks.

Stock markets in Japan dived to a two- month low, with the benchmark Nikkei 225 index slumping 3.5pc. In Hong Kong, the Hang Seng Index fell 2.54pc, while in China, the Shanghai Composite lost 0.78pc and the Shenzhen Index fell 1.1pc.