In January, British dealers made $2.2m (£1.7m) in web sales, with a 16% share of the global online drugs market.
However, US dealers had a 36% share of the online market and took home $5m (£3.8m).
Commissioned by the Netherlands government, research company Rand Europe trawled the eight largest drug marketplaces on the dark web.
These online shopping sites can be accessed only using a specialised web browser, and do not show up in mainstream search engine results.
Rand Europe found the number of drug deals taking place on the dark web had tripled since 2013, when police in the US closed Silk Road one of the first online drugs marketplaces.
Online deals still represent a small portion of the overall drugs trade, which Rand says is estimated to be worth £1.7bn a month in Europe.
Rand acknowledged that it faced difficulties collecting some of its data, due to the secretive nature of the online drug trade.
However, it suggested that a majority of deals were between buyers and sellers on the same continent, which it attributed to the popularity of locally grown cannabis.
List of biggest earners
United States – 35.9%
United Kingdom – 16.1%
Australia – 10.6%
Germany – 8.4%
Netherlands – 7.8%
Cannabis was the most popular item on the underground websites, accounting for a third of transactions.
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Purchases of prescription only medicines accounted for a further 19%.
The researchers noted that online transactions were dominated by “drugs typically associated with recreational or ‘party’ use” such as cannabis and ecstasy.
Offline, heroin is thought to account for 28% of the total European drugs retail market.
Rand said: “A possible explanation for these differences between online and offline markets may be that crypto market purchases typically require an element of planning, which may not suit the daily use of dependent users of, for instance, heroin.”