The fallout from the UK's vote to exit the European Union includes the risk of the pound losing favour as a place for safe-keeping by global managers and their $US11 trillion stockpile of reserves.

"To the extent that reserves serve as backstops against currency stress, rather than as sovereign wealth, the pound's diminishing role in international capital flows post-Brexit should permanently reduce its reserve status," Robin Winkler, a London-based Deutsche Bank strategist wrote in a note. "The pound may offer value, but is increasingly irrelevant."

The pound has depreciated 15 per cent since Briton's June 23 vote to exit the economic bloc, trading at $US1.26 on Wednesday. It reached $US1.1841 on October 7, the lowest since 1985.

The British currency's share of global reserves has fallen for the last two quarters to 4.5 per cent, according to the most recent International Monetary Fund quarterly Composition of Official Foreign Exchange Reserves report - dubbed as COFER data - which runs through September 30. The US dollar holds the largest slice at 63.3 per cent, followed by the euro with 20.3 per cent.

Research shows that global currency reserve allocations closely mirror the relative size of major currency blocs, Winkler wrote. These models show that the sterling grouping has already been cut in half since early 2015.

The slimming of the pound's share of reserves may be even worse than the IMF data may signal, given China only recently began to report allocations, added Winkler.

"We estimate that the pound's share has likely fallen from close to 10 per cent into low single digits since early 2015," Winkler said. This is consistent with the People's Bank of China "transitioning from wealth to currency management".

That doesn't bode well for the pound.