Sterling has continued to slide against the US dollar as trading reopened after Friday's record crash.
The pound dropped to 1.3409 dollars as markets resumed in Asia, a fall of more than 2% on top of the 10% plunge seen after Thursday's referendum.
Against the euro the pound was down 1.39% at 1.2149.
George Osborne will give a speech early on Monday in a bid to calm the market turmoil that spread globally after Britain voted to leave the European Union.
The pound slumped to its lowest level since 1985 on Friday after initially climbing steeply on the back of early suggestions Remain would win.