The NHS workforce shortage is forcing staff to work long hours with no breaks, and go lengthy spells without eating, drinking, sitting down or using the toilet. And when they are that hungry, exhausted and overstretched, they make mistakes.

This crisis comes after a year that, judged by any standards, was one of the worst in the history of the NHS. During a decade of decline, all the key indicators in the health service worsened, with more than 4.5 million patients now on waiting lists for treatment – more than ever before.

A shortage of doctors, nurses, beds and ongoing care facilities for elderly patients means patients on trolleys in corridors and levels of care that are far from safe are commonplace. Crises once confined to winter are now an all-year-round occurrence.

For anyone wondering whether the new decade will bring anything different, the first days of 2020 brought the news that A&E waiting times are the worst on record. Whatever the rest of this year brings in terms of the NHS workforce strategy, extra funding, or any other government policies, the health service will continue to teeter on the brink unless public health is made the focus.

Boris Johnson, both on the campaign trail and immediately after his election, insisted he would make the NHS a priority – with bold promises about new hospitals, doctor and nurse recruitment and investment in the NHS. But his pledges do not stand up to scrutiny.

NHS spending growth over the past decade has reached historic lows. Hospitals are building up huge deficits because they simply do not have enough money to treat patients.

But the most pressing existential threat to our NHS is the workforce crisis. Chronic staff shortages dramatically threaten the sustainability of the healthcare system. NHS trusts have more than 100,000 vacancies.

For patients, these staff shortages mean overfilled wards, long queues in A&E, three-week waits to see a GP and cancelled operations. For staff, they translate into burnout, depression, sickness and early retirement as they struggle to meet demand and expectations.

The NHS staff I meet tell me they love their jobs, and most wouldn’t do anything else; it’s a vocation to care for patients. But the level of stress endured by frontline NHS staff is unbelievable. Understaffing leaves them feeling isolated and strained. There is often pressure to take on more patients, to work extra shifts, to stretch themselves thinner and thinner. Trying to give care when you don’t have “enough” is heartbreaking. There is no longer enough time, staff or resources. It chips away daily and morale becomes broken. They are stretched because so many colleagues have left – left the country for places that support them better or left the profession altogether.

Understaffing begets poor morale, which further damages recruitment and retention. The number of personnel leaving the NHS because of a poor work-life balance has almost trebled between 2011-12 and 2018-19, according to analysis by the Health Foundation thinktank.

Continued understaffing could lead to even longer waiting lists, worsening care quality and the risk that the recent increase in NHS funding secured for frontline services will go unspent; even if commissioners have resources for additional activity, there may not be the personnel to deliver it.

The secret to the long-term sustainability of the NHS is to introduce a new model putting prevention rather than treatment at the heart of the healthcare system. This government must act where others have failed and take decisive action on smoking, alcohol misuse, physical activity and poor diet, underpinned by the introduction of policies to minimise the impact of the climate crisis and pollution on health and wellbeing.

Delivering a new model of healthcare will require well skilled and competent staff – not just public health specialists but also the wider workforce across health and social care. NHS organisations will need to develop an environment in which the workforce is given every encouragement to learn continuously.

The 1.2 million of us working in the NHS are struggling to do the right thing, but what will make the biggest difference for us – and for our patients – is a concerted focus on improving the population’s health.

• Kailash Chand chairs Healthwatch Tameside and is a former deputy chair of the British Medical Association council