The pound fell in the wake of Boris Johnson’s resignation from the Cabinet on Monday.
At 1500 sterling was trading at $1.3261, down 0.64 per cent from the $1.3346 level at 1440 when rumours of the Foreign Secretary’s departure began circulating.
Against the euro the pound was at €1.1287, down 0.43 per cent over the same period.
The move suggests the departure of Mr Johnson makes a no deal Brexit more likely.
Sterling slumped in February 2016 when Mr Johnson, after a long period of deliberation, announced that he would campaign for Brexit in the referendum.
Sterling had taken the overnight resignation of the Brexit Secretary David Davis largely in its stride.
Before this week sterling was trading at a seven-month low, as investors nerves frayed about the possibility of time running out for a viable Brexit deal with the European Union.