Sterling crashed 10 per cent to USD 1.3229 at one point, its weakest level since 1985, while the greenback itself slumped below 100 yen for the first time in two-and-a-half years as traders fled to safety.
In the weeks leading up to yesterday's historic vote, there had been widespread warnings that a 'Brexit' would cause a rout across global markets that would wipe trillions off valuations, just months after a painful China-fuelled sell-off.
Fears are also growing that other EU members will push for referendums, posing the biggest threat to the future of grouping since its inception almost 60 years ago.
The pound earlier topped USD 1.50 following predictions the "remain" group would win, but as the Brexit camp posted early victories around the country, traders stampeded to put in sell orders. In Asian afternoon trade it was at USD 1.3690.
More From This Section
"The extent of the damage on asset prices is hard to gauge but it's likely to be bigger than anything since Lehmans at the very least," he added, referring to the Wall Street bank whose collapsed precipitated the global financial crisis.
The dollar slumped briefly to 99.02 yen, the first time it has gone below 100 yen since November 2013, before edging back up above 102 yen.
Earlier Japan's Finance Minister Taro Aso vowed a "firm response" to volatility if necessary.
A flight to safety also saw higher-yielding and emerging market currencies slump, with the Australian dollar down 3.4 per cent, South Korea's won diving 2.4 per cent and the Indonesian rupiah shedding 1.7 per cent.
Malaysia's ringgit was down 2.7 per cent, one of its worst days since 1998.
As the shock results rolled in, equity markets went into meltdown, wiping hundreds of billions of dollars off shares.
Tokyo plunged nearly eight per cent, Sydney shed 3.2 per cent and Seoul was 3.1 per cent off. Shanghai sank 1.3 per cent, while Taipei, Wellington, Manila and Jakarta all saw sharp losses.