Of 1,000 cocaine users in England, and more than 500 in Scotland, more than a third said they could get the drug delivered within half an hour.
Around 36.8% of people surveyed in England said they could get cocaine within 30 minutes, and 37.4% in Scotland, placing them fifth and sixth in the world rankings.
This compares with 12.2% of people in England and 19.8% in Scotland who said they could get a pizza delivered in this time.
Across the world, 30.3% of 15,000 cocaine users questioned for the 2018 Global Drug Survey said they would be able to get their hands on the drug within half an hour.
Only 16.5% said they could get a pizza delivered in that time.
The report said dealers were competing for customers not only through product quality but through speed of delivery, with easy access and higher purity “likely to lead to escalating use and harms among people”.
“With many cities covered with CCTV cameras, traditional street dealing is becoming less attractive to many suppliers and consumers,” it added.
“On the other hand, darknet markets allow drugs to be delivered through your letterbox and the rise of encrypted social media platforms makes ordering relatively safe.
“Thus, it’s not surprising that the next customer service upgrade was going to be the growth of sophisticated and rapid drug delivery services in many of our big cities.”
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The report surveyed 130,000 drug users across 44 countries, including more than 5,000 in the UK, about recreational drug use and its impact on health.
Drug users in England were found to consume the second-highest amount of cocaine in a single session (0.7g), beaten only by Scotland globally.