One in five adults in St Helens were prescribed highly addictive opioid painkillers last year, a new report reveals.
Health secretary Matt Hancock has said the country is "in the grip of an over-medication crisis", and pledged to take immediate steps to address the issue.
Public Health England figures show that 28,222 adults in the St Helens Clinical Commissioning Group area received at least one prescription for opioid painkillers in 2017-18 – 20% of the adult population.
Three in five residents on a prescription for the drugs during March last year had been taking them for a year or more, the study found.
The figures exclude people who were prescribed opioid painkillers for cancer pain.
Mr Hancock said he was "incredibly concerned" by the findings of the review, which found that 5.6 million people across England were prescribed opioids in 2017-18.
He said: "The disturbing findings of the report, especially that one in eight adults in England are taking super-strength, addictive opioid painkillers, many for extended periods of time, prove to me that we are in the grip of an over-medication crisis.
"What is equally alarming is that in many cases, these medicines are unlikely to be working effectively due to over-use.
"I refuse to let this escalate to the level seen in the United States. To be clear, the entire healthcare system will now be involved in making sure we put an end to this, once and for all."
Opioids are known to be ineffective for most people over the long term, but many patients struggle to come off the drugs.
Although PHE was unable to put a figure on how many people were addicted to the painkillers, it said patients must be warned via a national helpline about dependency risks, and receive advice on coping with withdrawal.
The review also examined prescribing rates for anti-depressants, anti-anxiety drugs and sleeping pills.
In St Helens, 33,783 people received a prescription for anti-depressants in 2017-18 – 24% of the adult population.
Gabapentinoids, such as pregabalin, used to treat epilepsy, nerve pain and anxiety, were prescribed to 6% of adults, and 5% received benzodiazepines, such as diazepam, for anxiety and insomnia.
And 4% of adults collected a prescription for sleeping pills, or Z drugs. People prescribed multiple medicines will be counted more than once in the figures.
Professor Helen Stokes-Lampard, chairwoman of the Royal College of GPs, said: "This study indicates the severe lack of alternatives to drug therapies for many conditions, and where effective alternatives are known and exist, inadequate and unequal access to them across the country.
"There are wide-ranging and complex issues surrounding the prescribing of opioids and anti-depressants.
"GPs don't want to prescribe medication long term unless it is essential, but there will always be some patients for whom medication is the only thing that helps with distressing conditions such as chronic pain, or depression and anxiety."
Across England, 11.5 million people, more than a quarter of the adult population, collected one or more prescriptions for any of the five medicines included in the review.