Bitcoin and rival cryptocurrencies all lose value after Google bans advertising

Ethereum, litecoin and bitcoin cash all slump after torrid week

The price of bitcoin and its competitors has fallen dramatically over the last three days, with all but two of the top 50 cryptocurrencies further tumbling in value this morning.

Bitcoin, ethereum, ripple and bitcoin cash have all dropped in value by at least 7 per cent in the last 24 hours, according to CoinMarketCap, having slid steadily since Monday.

One bitcoin is worth $8,118 (£5,826) at the time of writing, down 7.15 per cent compared to Wednesday morning, 13.48 per cent on this time last week and 4.41 per cent on mid-February, going by Coinbase data.

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Of CoinMarketCap's top 50, only tether and digixDAO - two comparatively obscure coins - saw any growth at all.

The biggest slumps were suffered by nem and steem, which lost 25.06 per cent and 17.93 per cent of their values respectively in 24 hours.

The virtual currency market has endured a torrid week, with Google announcing plans to cull cryptocurrency advertising from its search results, purging initial coin offerings and other speculative investment promotions on the grounds that they represent "deceptive content" consumers cannot trust.

The crypto-sector was also prominently mocked by John Oliver on his popular HBO show Last Week Tonight and saw security questions raised after an attempted heist on China's Binance exchange.

Binance has since offered a $250,000 (£179,000) bounty for information that led to the thieves' arrest, a gesture doing nothing to quell comparisons between the unregulated digicoin scene and the Wild West.

The spectre of regulation continues to cast a shadow, with India's former Economic Affairs Secretary Shaktikanta Das the latest to reassert doubts about the market's safety, arguing that online coin transactions were too complex to regulate and should instead be banned outright.

China and South Korea have expressed similarly conservative attitudes towards cryptocurrencies in recent months.

Bitcoin still dominates the market with a 42.2 per cent share but is increasingly being challenged by the impressive performance of its nearest rivals and today's declines again underline the core vulnerability of an industry still in its infancy and still very much open to question.

Bitcoin's pre-Christmas boom in value to $19,850 (£14,214) suddenly seems a long time ago.