Image copyright Jen McAdam

A woman has received death threats after speaking out about an international cryptocurrency "scam".

Jen McAdam, from Glasgow, has been leading a band of investors who believe they have been duped by the OneCoin digital currency.

OneCoin is said to have raised as much as £4bn around the world in investment.

But US prosecutors argue that far from being the next Bitcoin, OneCoin is a pyramid scheme masquerading as a cryptocurrency.

The scheme's founder Dr Ruja Ignatova has disappeared and is facing money laundering charges.

Ms McAdam is one of an estimated 70,000 people in the UK who bought packages from OneCoin but have been unable to trade or fully cash in their stake.

The Bulgaria-based firm is still trading and denies any suggestion OneCoin is a scam, claiming it fulfils all criteria of the definition of a cryptocurrency.

'Vile abuse'

Ms McAdam is taking part in the 'Cryptoqueen' BBC Sounds podcast which is investigating the disappearance of Dr Ignatova and OneCoin, and said she has had a torrent of abuse since.

The 49-year-old revealed she has received scores of messages, mainly through Facebook, threatening her with sexual violence and death in what she claims are co-ordinated attacks by OneCoin supporters, and has now reported the threats to Police Scotland.

She said: "It is horrible, the abuse is vile and the threats feel very real to me, I'm always looking over my shoulder now.

"It is taking its toll on my health but I will not give up until me and the thousands of other OneCoin victims like me see some form of justice."

Image copyright YouTube Image caption At a big event at London in 2016, Dr Ruja Ignatova talked up her cryptocurrency OneCoin to supporters

Ms McAdam invested about £8,000 of her own money in the scheme, and persuaded family and friends to put in about £220,000, before realising she was not going to get the money back.

"I know through the different victims' groups around the world that it is people just like me who are affected," she said. "They invested their life savings, they remortgaged homes and they convinced their friends and family to get involved -and they feel as awful as I do about it all because we were all duped.

"We think there's around 70,000 victims in the UK but it feels as if they are being left behind, nobody here seems interested in this."

Ms McAdam has called on the UK policing and financial regulation authorities to take the issue more seriously.

'Pyramid scheme'

The Cryptoqueen podcast estimates OneCoin has raised as much as £4bn from people in 175 countries, with up to £96m in the UK alone.

The flamboyant leader of OneCoin, Dr Ignatova, disappeared in 2017 and in March this year US prosecutors charged the Oxford-educated businesswoman in absentia with money laundering, with the Department of Justice calling OneCoin an old-fashioned pyramid scheme.

New York County District Attorney Cyrus Vance was reported as describing OneCoin as "an old-school pyramid scheme on a new-school platform".

What is cryptocurrency?

Image copyright Getty Images Image caption Investment in cryptocurrencies has soared since Bitcoin was invented in 2008

An alternative to centuries-old forms of currency such as notes and coins, a cryptocurrency is like a virtual token which can be bought and sold on the internet.

The currency is not printed by governments or traditional banks but created through a complex process known as "mining".

The process is monitored by a network of computers across the world which use cryptography for security.

Cryptocurrencies can be used to buy goods and services, like traditional currencies, but are also used as investments where people take advantage of their volatile exchange rates.

Bitcoin is probably the most famous cryptocurrency but there are now thousands of the standalone digital currencies, with Facebook looking to launch its own too .

But as OneCoin has proved, crypto can be more controversy than currency.

Research published on 7 October showed that UK regulator the Financial Conduct Authority was conducting 87 investigations into the sector as of September, up from 50 a year earlier.

OneCoin has rejected allegations that it is a scam, and states that "OneCoin verifiably fulfils all criteria of the definition of a cryptocurrency".

It says the BBC podcast series into its business does "not present any truthful information and cannot be considered objective, nor unbiased".

The company also claims that the allegations made about it around the world are being challenged, stating: "Our partners, our customers and our lawyers are fighting successfully against this action around the globe and we are sure that the vision of a new system on the basis of a 'financial revolution' will be established".

A Police Scotland spokeswoman confirmed they had visited Ms McAdam and offered her advice in the wake of the anonymous threats against her.

You can listen to The Missing Cryptoqueen podcast series on BBC Sounds.