Cuts to publicly funded drug and alcohol treatment have contributed to a 26% rise in drug-related deaths, an addiction service has said.
Analysis by the BBC found £162m (18%) has been cut from treatment budgets in England since 2013-14.
Privately-run UK Addiction Treatment (UKAT) said addicts were being left "on their own" as councils plan more cuts.
The government said addiction services remained free with "minimal waiting times".
In 2013 there were 2,734 drug poisoning deaths in England, rising to 3,450 in 2016, official figures show.
Real terms budgeted spending on drug and alcohol treatment services fell from £877m in 2013-14 to £716m in 2017-18.
One former addict told how her calls to a drug treatment service went unanswered, forcing her mother to take drastic action.
'One of the lucky ones'
Mel Curtis lived a double life, holding down jobs as a PA and then an operations manager in London, whilst secretly battling a near fatal addiction to alcohol and cocaine.
"It was just a complete nightmare," said the 38-year-old from Hertfordshire.
"Two years ago my drug abuse led me to the point where I was trying to kill myself and my mum effectively had to put me under house arrest.
"All my GP could do for me was give me some anti-depressants and a phone number for the local drug treatment team. When I rang that number nobody answered. I rang the drug treatment service repeatedly but got nowhere."
Ms Curtis said she considered herself one of "the lucky ones".
"I've watched people close to me die because of their addictions," she said. "They've asked for help but it's just not been there."
Every nation in the UK has seen a rise in the number of drug-related deaths in the past decade, with 4,737 drug-related deaths recorded across the UK in 2016 compared with 3,082 in 2006.
Eytan Alexander, the founder of UKAT, said cuts to spending had resulted in fewer people getting the help they need.
"These cuts are killing people," he said.
"Councils used to be able to fund places in long-term residential treatment centres, but money is now being spent on cheaper community-based services. This means addicts receive treatment during the day, but when they return home, they're on their own and are more likely to relapse.
"The worst bit is that these cuts are only going to get worse."
UKAT's own research has found that two thirds of the councils in England that responded to a Freedom of Information request said they planned to make further cuts to spending on treatment services for the financial year 2018-19.
Figures from Public Health England (PHE) show that since 2013-14, when local authorities became responsible for providing drug and alcohol services, there has been a 7% fall in the number of people accessing treatment.
The latest figures for 2016-17 show 279,793 individuals were in contact with drug and alcohol services, down from 301,944 in 2013-14.
The BBC England Data Unit has analysed how much local councils in England budgeted to spend on providing treatment services, between 2013-14 and 2017-18:
- Seven out of 10 councils in England made cuts to the amount they planned to spend on drug and alcohol services.
- Of those councils who reduced spending on drug and alcohol treatment services, 83% saw an increase in drug-related deaths.
Figures published by the Scottish Parliament show the Scottish government reduced its spending on drug and alcohol services by 14% in cash terms between 2015-16 and 2017-18.
Spending on treatment services in Worcestershire has halved in the past four years while the number of drug-related deaths increased by 43%.
Worcestershire County Council said the reduction in spending was due largely to the provision of treatment services for prisoners being transferred to the NHS.
A spokeswoman added: "The number of drug-related deaths is increasing nationally, partly due to a rise in the availability and purity of heroin and an aging population of heroin users."
'Filling a void'
The town of Barrow in Cumbria has seen a spike in drug deaths, with 12 people dying in the town between December 2017 and April 2018.
Cumbria County Council has reduced its spending on treatment services by a third in the past four years.
"I've never had a voter come up to me and say we should spend more money on drug treatment services," said Cumbria council's deputy leader, Ian Stewart.
Mr Stewart is also the County Council Network spokesman for public health and said the 37 councils he represents are struggling under the government's austerity programme.
"We have to make really difficult choices when it comes to spending money on the services people really want, which is made harder when the government takes £200m out of the public health budget in just one year," he said.
"It's too simplistic to say cuts in spending are causing more deaths, but I do feel that years of government austerity have left a void, that has been filled in some communities by drugs and alcohol."
'Drug use lower'
Overall drug use has been falling in England and Wales in the past decade, according to the annual crime survey.
In 2006-07 10.1% of people aged 16 to 59 admitted using an illicit drug in the previous 12 months. In 2016-17 that proportion had fallen to 8.5%, an estimated reduction of 380,000 people.
The UK government's latest drug strategy, published in 2017, put an emphasis on reducing all illicit and other harmful drug use.
A spokeswoman for the Department of Health & Social Care said: "While drug misuse is lower than 10 years ago, we remain committed to reducing it. Addiction treatment services remain free for all with minimal waiting times.
"We are investing £16 billion in local public health services and our comprehensive drug strategy brings together police, health and global partners to help those with drug dependency recover and turn their lives around."