The pound has fallen below $1.29 for the first time in almost a year on continuing worries Britain will leave the EU without a trade deal.
Sterling also hit a nine-month low against the euro, and was down against the yen and Swiss franc.
Bank of England governor Mark Carney said on Friday the chances of a no-deal Brexit were “uncomfortably high”.
On Sunday, international trade secretary Liam Fox put the odds at “certainly not much more than 60-40”.
The falls come despite a rise in UK interest rates, which usually pushes up the value of sterling.
Since the beginning of the month, the pound has fallen 1.7% against the dollar and 0.8% against the euro.