It represents a six-fold increase in drug users escaping prosecution since 2016, when the proportion was only 7.5 per cent.

In some forces, more than 80 per cent caught with cocaine, heroin or other class A drugs escaped any criminal punishment.

They were instead handed community resolutions, which do not result in a criminal record and only require an offender to accept “responsibility” for their crime, or were let off “in the public interest”.

Only a third of class A drug possession offences resulted in a charge.

But critics have warned police against “decriminalising drugs via the back door by ignoring tens of thousands of offences”.

At least a quarter of the 43 police forces in England and Wales have adopted “diversion” schemes where users caught with small amounts of drugs like cannabis are “diverted” to treatment or education programmes rather than prosecuted, particularly for first-time offences.

Nearly three-quarters (72.1 per cent) of those caught in possession of cannabis were let off without any criminal sanctions.

The Treasury and Cabinet Office have put £1.9 million into evaluating the approach in partnership with five universities, the National Police Chiefs’ Council (NPCC) and the College of Policing, the standards body for forces in England and Wales.

The College said the aim of the diversion scheme was to “reduce re-offending and wider harms by approaching substance use as a health issue rather than a criminal justice issue”.

The research will compare re-offending rates, hospital and treatment admissions with the aim of establishing “whether and how drug diversion works, for whom, when and why”.

‘Devastated by soft policy’

But Chris Philp, the Tory shadow home secretary, warned the move amounted to decriminalisation by stealth.

“Parliament has rightly legislated that certain drugs are illegal because they cause serious harm to health, lead to antisocial behaviour and fuel acquisitive crime like theft, burglary and shoplifting as addicts steal to fund buying drugs,” he said.

“Police should not be decriminalising drugs via the back door by ignoring tens of thousands of offences. People who break the law should be prosecuted, and a magistrate or judge can decide what to do.

“Options a magistrate has available include fines, community service and addiction treatment requirements as well as prison.

“We have seen many US and Canadian cities devastated by soft drugs policies. These have allowed ghettos to develop where zombified addicts loiter unpunished and law abiding members of the public fear to go. We can’t allow the UK to go the same way through weak policing.

“We need a zero tolerance approach to crime, including a zero tolerance approach to drug taking.”

But the College of Policing defended its approach and pointed to research, based on 16 different studies, that showed drug diversion had resulted in a “small but significant” reduction in drug use, particularly among young people.

The Telegraph analysis showed that Warwickshire had the lowest proportion of offenders caught with class A drugs who were let off, at just 9.2 per cent, while Dyfed Powys had the highest at 88.6 per cent.

Nerys Thomas, Director of Research at the College of Policing, said:“We are focussed on cutting crime and keeping the public safe. Class A drugs are the most harmful category and being found in possession of them is a criminal offence.

“The government has provided funding to understand what initiatives could be used to reduce offending and protect the public. This includes a piece of work between the College,  the University of Sheffield and 11 other agencies across the criminal justice system to interview hundreds of officers and drug offenders and analyse police data to understand if diversion schemes can reduce crime.

“The results of this study will be made publicly available next year.”