Sterling skidded lower this afternoon after British foreign minister Boris Johnson resigned, with the pound falling against both the dollar and the euro.
Johnson followed former Brexit minister David Davis in resigning.
Davis had resigned last night in opposition to Prime Minister Theresa May's plan for life after leaving the European Union.
The pound fell from around $1.3340 to trade as low as $1.3259, down 0.2% the day, after news of Johnson's resignation.
Against the euro, sterling fell 0.4% to trade down at 88.62 pence per euro.
"What we say is the pound can handle ministerial resignations if that's the extent of it... if it means Johnson leaving and not launching a leadership challenge," ING strategist Viraj Patel said.
He added, however, that a leadership bid by Johnson would open up further uncertainty.
Britain's internationally-exposed FTSE 100 extended gains slightly as the pound weakened.