Sterling carved out a fresh 31-year trough on Wednesday while the safe-haven yen soared on heightening fears of the broader impact of Britain's vote last month to exit the European Union.
The pound slid as far as $1.2798 breaking through the previous low of $1.3000 set overnight.
It was last down 1.2 percent at $1.2867.
The euro jumped as high as 86.26 pence its highest since August 2013, and was last up 0.9 percent at 85.76 pence.
Against the resurgent Japanese currency, sterling fell as low as 128.81 yen its lowest since November 2012.
It was last down 2.2 percent at 129.61.