Until a week ago, financial markets and London-based authorities had regarded the risk of Scotland's departure as unlikely.
Sterling sank more than 1 percent, its most in 13 months, to trade above $1.61 against the dollar. It was also almost 1 percent lower against the euro, driving the Bank of England's trade-weighted sterling index to its lowest since the end of April.
The dollar index rose to its highest levels since July 2013 as the Australian dollar and Brazilian real also dropped against the currency.
The Australian dollar fell 0.96 percent to roughly US $0.93, backing off from Friday's level above $0.94, its highest since late July.
The Aussie has shown resilience despite recent U.S. dollar strength and a sharp decline in prices of iron ore, Australia's top export earner, in large part due to renewed carry trade demand. Investors are borrowing at low rates in euros and yen to buy higher-yielding Aussie assets.
The Brazilian real fell 0.05 percent as the country's presidential race was shaken up by a corruption scandal that allegedly involves state-run oil firm Petrobras and dozens of lawmakers, with both leading candidates forced onto the defensive after colleagues were implicated.
The greenback has gained despite disappointment over Friday's U.S. employment report for August.
The euro fell slightly against the dollar, after coming under pressure on Thursday after the European Central Bank cut rates to new lows and launched an asset-purchase program to ward off deflation, and some see it as likely to continue to decline.
Market positioning still indicates a number of investors are short the euro zone currency, which is likely to weigh further, said Schwerdtfeger. ``It's very hard to find anyone at the moment that is trusting that the euro is going to go higher.''
The euro was last above $1.29, just off a 14-month low set on Thursday.
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