We are living in a world in which the politics of the leaders of two of the world’s great nations – America and Britain – is built on broken promises. During Donald Trump’s election campaign he promised to “take on Wall Street”. So when just weeks later the president announced a cabinet full of banker billionaires, my brother, Senator Bernie Sanders, said: “With all due respect, Donald Trump is a fraud.”

Meanwhile, here in the UK Theresa May took up her post as prime minister on the commitment to “work for all, not just the privileged few”. Well, it is just weeks since our NHS descended into a humanitarian crisis, and we are already looking at another round of privatisation and cuts. Which is why at midday today we will be marching on parliament in support of the NHS.

We don’t need reminding of the horrors we saw over the winter, with people dying on trolleys and turned away from hospitals, and the British Medical Association warning our most cherished institution has been pushed to breaking point. The NHS is facing a £22bn funding gap, with the demand for care set to rise 4% a year while the health service’s budget will go up by only 0.2% every year between now and 2020.

This crisis in healthcare has been exacerbated by the current Tory government – but its foundations were laid by New Labour and further strengthened by the coalition with the Health and Social Care Act of 2012. The creeping privatisation of the past quarter of a century has introduced vast fragmentation and inefficiency into our health service, and, combined with chronic underfunding, has left the NHS on the brink. Anyone who has visited a hospital recently knows how hard doctors, nurses and all the staff are working to make sure patients are cared for with dignity and compassion, despite the strain on the system. It is time we listened to their concerns.

Adding to the pressure facing hospitals across the country is the financial crisis in social care. We’re living longer, and that’s a great thing – last year, aged 81, I stood in the Witney byelection after David Cameron resigned. But while there are currently one-third more over-85s than 10 years ago, adult social care budgets have been cut by one third in the same time. And the care funded by local authorities accounts for just a small proportion of the care elderly people in the UK currently receive. Every year family, friends and neighbours provide £55bn of unpaid care, four in 10 people in care homes pay for themselves, and a staggering 1.2 million people over 65 with care needs receive no help at all.

We are simply not providing enough care and support for people in the community, at home and close to where they live. This means elderly people are more likely to end up in hospital, and when they get there it is more difficult to get them home again. People who are medically well are stuck in hospital because there is nowhere suitable for them to go and too little support for them at home. The system is failing these people who could be living at home or in supported accommodation instead of being isolated from their communities on a hospital ward. But it also fails those who desperately need the hospital beds these elderly people occupy.

The government’s response has been to engage in a cruel con where local councils were told there was “new” funding for social care, only to find much-needed funding cut from elsewhere. It is little wonder the system is on its knees – and the prime minister’s insistence on ending free movement as part of Brexit risks starving the NHS and care services of the staff they so desperately need.

Today thousands of people will march in support of the NHS, unwilling to stand by and watch while this government dismantles public healthcare – and I’m proud to be among their number. The government tells us there isn’t enough money but this isn’t true. We are the fifth richest country in the world – we have the money to stop our health service turning into a humanitarian crisis, and to care for people when they grow old: in hospitals, the community and homes. We have the money for a fully funded public health service. If Theresa May is to keep her promise to “work for all, not just the privileged few”, she must not let the NHS and social care crumble on her watch.