I have worked as a GP over the past decade in about a third of the around 140 prisons in England and Wales – all categories, male and female – and in all there has been a gradual increase in the prison population, leading to overcrowding.

This reflects the national situation. Ministry of Justice figures show that between June 1993 and June 2012 the prison population in England and Wales increased by 41,800 prisoners, to more than 86,000. Without urgent steps aimed at cutting the prison population this could exceed 100,000 by 2020. However, this has not been matched by a corresponding increase in the number of prison officers. On the contrary, their numbers have been cut.

When our prisons are at crisis point, amid continuing controversy about incidents such as the recent killing at Pentonville, consider our direction of travel. Take HMP Berwyn, the so-called super prison expected to open in February 2017.

Built at the cost of £212m and located at Wrexham in Wales, HMP Berwyn is expected to accommodate 2,100 category C prisoners – those who cannot be allowed to move freely but are considered unlikely to try to escape. Instead of taking steps to radically reduce the UK prison population the government keeps building more prisons to house even more prisoners.

I have come across numerous cases over the years where a noncustodial sentence would have been more appropriate than imprisonment. I recall a heavily pregnant lady suffering from a life-threatening condition who was jailed for breaching a restraining order. What was to be expected of a pregnant sufferer confined for a good deal of the time in a small, poorly ventilated prison cell? During her time behind bars she was rushed to hospital several times. Whenever she was there, for sometimes up to a week and longer, she was guarded round the clock by prison officers.

I recall another instance when the nurse, seeing the new arrivals on reception duty, sent me the following message, asking me to prescribe a short course of sleeping tablets for a recent arrival. She was in prison for failing to pay a bill. Her partner was supposed to be looking after their young children but, the message said: “she does not believe he is up to the task. She is in a very weepy state and unable to sleep. She has another four weeks to do – could you please help?”

These women represent a not insignificant proportion of the prison population who are not a “danger to the public”. So why is the state spending large sums to keep them behind bars?

Ministry of Justice figures from 2013 revealed that 55% of prisoners connected their offences to drug-taking, with the need for money to buy drugs the most commonly cited factor. Eliminating the addiction factor could lead to the closure of about half the prisons in the UK and free resources for other matters.

Sending these people to jail in the hope of ridding society of the menace of drug abuse is a woefully inadequate approach to the complex problem of drugs. It is akin to a doctor treating the symptoms of a disease without concerning themselves with its cause or its future prevention. There should instead be a holistic approach to the problem of drug addiction, with treatment and rehabilitation forming the centrepiece.

And then there are the inmates with mental health issues. Surely these are best handled in psychiatric institutions rather than prison. Instead of spending millions on “super prisons”, the state would be better employed building additional psychiatric hospitals and homes to accommodate the hundreds, if not thousands, of them languishing in jail. Instead of helping them to overcome their mental impairment, society is punishing them for a condition they cannot help having. Labelling them criminals on a par with those who commit armed robbery, rape and murder is antiquated at best and nonsensical at worst. Samuel Butler lampooned this stance in his classic satire, Erewhon, describing a culture who imprisoned the sick for the crime of not being well. That was published in 1872, but what has changed since then?

A report published last month by the RSA’s Future Prison project says the prison and probation services in England and Wales are failing to protect the public because they do not rehabilitate offenders, and that they should be radically restructured. I welcome the rehabilitation aspect, but it still ignores the central issue of population.

We need urgently to address sentencing, because too many offenders are being sent to prison for short terms. A record-breaking case was that of a lady who was jailed one evening only to be released the next day. I believe any sentence below three months should be suspended, turned into fines or whatever other punishment society deems appropriate short of an actual prison sentence.

As for drug addicts, the power to sentence them to drug rehabilitation homes makes sense for everybody. Keeping the most dangerous criminals – sex offenders, murderers, terrorists, armed robbers, and so on – in jail, and finding alternative punishment for those committing petty crimes, would not only lead a radical reduction in the prison population, it would also allow for the proper supervision of extremely dangerous inmates.

Whatever else is said this week, population reduction is where our focus is and it is quite achievable. What is really needed is the will.

• Dr Gordon Cameron is a pseudonym. Memoirs of Her Majesty’s Prison Doctor by Dr Cameron is available now. Visit hmpdoctorsmemoirs.com