A leading cryptocurrency expert on Wall Street has tipped the Ether digital currency to rally after a steep fall in value in 2017.

Tom Lee is the co-founder of Fundstrat, which advises institutional investors, wealth advisors, pension funds and high net worth individuals on the markets.

Ether has lost 70 percent of its value this year – and dropped 50 per cent in the last three months alone – after a stellar 2017 in which it outperformed even market leader Bitcoin.

Former J.P. Morgan chief equity strategist Lee said recent history shows that Ethereum – the blockchain on which Ether is based – is “about to rally strongly”.

"We believe Ethereum is about to stage a trend reversal and rally strongly," he said in a note to clients on Thursday.

Lee said on the previous four occasions that Ether faltered compared with other digital currencies, it staged a "major trend reversal" – and added that “sentiment is currently overly negative on ETH".

The real-world uses for the Ethereum blockchain led many to predict last year that Ether would eventually overtake Bitcoin as the world’s most valued cryptocurrency.

Yet blockchain developers now have EOS – which was built on Ethereum before switching to its own token. EOS is now the fifth most valuable cryptocurrency.