UK-based dealers in illegal drugs earn more money online than any of their European rivals, research suggests, while US dealers had a 36% share worldwide and took home $5m (£3.8m).
In January, British dealers made $2.2m (£1.7m), 16% of the online market.
Commissioned by the Netherlands government, research company Rand Europe trawled the eight largest drug marketplaces on the dark web.
These online sites can be accessed only using a specialised web browser.
They 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.
Cannabis was the most popular item on the underground websites, accounting for a third of transactions.
Purchases of prescription-only medicines accounted for a further 19%.