The Catalan capital came out tops of where cocaine is most used in a  wastewater analysis study of 56 European cities in 19 countries undertaken by sewage analysis centre Score and the EU drugs agency in March 2017.

The study analyzed daily wastewater samples in the catchment areas of treatment plants over a one-week period, testing the wastewater of 43 million people for traces of four drugs: amphetamine, cocaine, MDMA (ecstasy) and methamphetamine (crystal meth).

The results, released by the European Monitoring Centre for Drugs and Drugs addiction (Emcdda) on Wednesday, show that cocaine is used most in Barcelona on a daily basis, although it is beaten by Zurich at weekends.

In terms of cocaine usage, the analysis revealed, on average, Barcelona gets through 965.2mg each day for every 1,000 residents.

This is the highest amount since records began in 2011.

In a press release, the Emcdda said cocaine use is highest in western and southern European cities, with data suggesting use of the drug is on an upward trend. However cocaine use in the majority of eastern European cities is very low to negligible.

But while in Barcelona, cocaine is the recreational drug of choice, the city also appeared at number 7 on the list for Ecstasy (MDMA).

It was the only Spanish city to rank in the top ten for any of the drugs tested.

Surprisingly, Switzerland had five cities that ranked in the top ten for cocaine use.

The study found that levels of cocaine and ecstasy in wastewater rise sharply at weekends in most cities, while amphetamine use appears to be more evenly distributed throughout the week.