Deaths due to drug misuse have more than quadrupled since 1993, the earliest year on record - from four, to 23 deaths in 2019.
Misuse accounts for the vast majority of total drug poisoning-related deaths in the borough, at 82 per cent, according to the Office for National Statistics (ONS).
The latest figure for Barnsley is the third-highest of the four South Yorkshire authorities, with Rotherham recording three less deaths due to misuse.
But when the definition is widened to drug poisoning, Barnsley recorded the lowest number of deaths in the region at 28 last year - despite this still being an almost three-fold increase since 1993.
To be classified as drug misuse, a death must be a drug poisoning caused by an underlying abuse or dependence issue, or involving substances controlled under the Misuse of Drugs Act.
These include opioids, cannabinoids - such as ‘spice’ - sedatives, stimulants, cocaine and various other psychoactive or hallucinogenic substances.
The definition also covers mental and behavioural disorders caused by volatile solvents, accidental or intentional poisoning, or assaults involving substances.
Men account for more than twice as many drug-related deaths as women, with 57 deaths registered between 2017 and 2019 compared to 21 for females.
This rises to more than three times as many with regards to deaths due to drug misuse, with 37 deaths in men and 12 in women across the same two-year period.
Nationally and regionally, numbers of drug poisoning-related deaths are the highest since records began - with Yorkshire and the Humber accounting for more than one in ten drug deaths in the total recorded in England and Wales.
Nuno Albuquerque, group treatment lead at UK Addiction Treatment Group - which has just purchased Linwood House rehabilitation centre in New Lodge - said: “These ONS figures are saddening but unsurprising.
“It is here in black and white, the situation is only getting worse for those most vulnerable in society.
“We must remember that these aren’t just numbers - they’re someone’s mother, father, child or friend who has lost their lives to drugs and we can’t stress enough the value of investing in the treatment of addiction.
“2020 has proven to be a difficult year for many.
“Some will undoubtedly turn to misusing drugs as a coping mechanism.
“Our fear is that these figures could tip off the scale in next year’s report unless councils here take proactive, preventative action today in order to save lives tomorrow.”
Coun Jenny Platts, cabinet spokesperson for adults and communities, said: “We aligned our drug and alcohol services back in April 2017; this meant that we were able to deliver a better service for people in Barnsley, while also adjusting to budget pressures.
“These services have been successful and provide integrated support for residents who need it the most. We are currently undertaking a strategic review of substance misuse and the findings from this will inform and shape future provision.”
Numbers of children referred to social services due to drug and alcohol problems are likely to rise following the Covid-19 lockdown, according to UKAT.
Department for Education figures listed 1,924 cases that were referred and deemed to require further assessment last year. Of these, 183 were for alcohol misuse, and 286 were for drug misuse.
According to Public Health England figures, 115 cases of drug misuse in 15 to 24-year-olds were seen last year by doctors at Barnsley Hospital - a rate of 143.1 per 100,000 people, higher than any other town or city in the region.