It is becoming sadly clear that the crisis engulfing the NHS will be the worst we’ve seen for many years. GP surgeries are full and hospitals are at breaking point. The shortage of social and community care means that a small problem for an older person quickly escalates into a hospital admission, and many who no longer need to be in hospital cannot be discharged. This week we learned that non-urgent operations in hospitals in England will be postponed until after January.

Huge credit must go to the staff who have worked over the holiday period to manage this crisis. Doctors, nurses, paramedics, community teams, social workers and even managers are giving their all to patients. We all owe them a debt of gratitude, but what they really want is to be able to do their job with adequate resources.

Having worked in the NHS for 17 years as a GP, I know that the causes of this crisis are complex and multi-faceted. People are living longer; there are major staff and skills shortages; social care provision is inadequate and too disconnected from the health service; budgets are under severe strain; and the extra money provided by the government for this winter was far too little, and far too late.

But what is increasingly clear is that the biggest – and perhaps even an existential – threat to the NHS is Brexit. Clean, hard, soft, deal or no deal – whatever the government comes back with from Brussels later this year, Brexit is already damaging the NHS and will be a stress multiplier for all the challenges facing the health service for decades to come.

Leave campaigners promised that by voting to leave the EU, the public would be delivering a £350m a week cash injection to our most treasured national institution. The reality is quite the opposite. To date Brexit has in fact cost around £350m a week in lower growth. And that’s before the £40bn divorce bill and the many years of anaemic economic growth that lie ahead.

The weakening of our currency, falling investment and business uncertainty are suffocating our economy, taking us from being the fastest growing economy in the G7 before the referendum to the slowest today. While the NHS is crying out for more money, we are systematically downgrading our economy.

And the “sunlit uplands” promised by ministers show no sign of materialising. A Canada-style free trade agreement, which is the only option available to the government now it has ruled out remaining in the single market, would be devastating for the public finances. Philip Hammond himself said during the referendum that the Canada deal “does not even remotely replicate the access we have as an EU member,” and the Treasury has predicted it would hit GDP by 6.2 per cent by 2030.

Be in no doubt that the impact of this will be lower tax receipts, more austerity and ever-tighter budgets for the NHS and other public services.

As the funding crisis deepens, Brexit is also exacerbating staff shortages. The uncertainty felt by EU nationals, coupled with the fall in the value of the pound, has led many to reconsider whether this is the country for them. Almost 10,000 EU NHS workers have already quit since the Brexit vote. Almost one in five of the NHS’s European doctors have made plans to leave the UK, according to a survey by the British Medical Association. And there has been a 96 per cent drop in EU nurses registering to work in Britain since the Brexit vote.

It cannot be overstated how vital nurses and doctors from the EU are to keeping the health service running. Much more must be done to train more doctors and nurses in Britain, but this will take many years. The NHS simply will not survive an exodus of European staff.

Meanwhile, a weaker currency also means a greater share of the health service’s budget is being swallowed up on importing medicines and equipment. At least half of the products used in the NHS originate from outside of the UK, and with the pound around 15 per cent down against the Euro since the referendum, those imports cost significantly more today than they used to. While data on this is yet to emerge, a study in July 2016 predicted that this could create a £900m a year shortfall, meaning less money for patient care.

Under these stresses and strains, demands from the Tory Right will grow for the NHS to be privatised. Indeed, this is what many of those who campaigned for Brexit have always wanted. Former Prime Minister John Major, who knows as well as anybody about the real agenda of the Brexiteers, warned last year of the risk of NHS privatisation under Leave campaigners like Boris Johnson, Iain Duncan Smith and Michael Gove. “The NHS is about as safe with them as a pet hamster would be with a hungry python,” he said. We should all take heed.

With new facts about Brexit and its impact on the NHS coming to light all the time, everyone has the right to keep an open mind about whether this is the right future for our country and our health service.

5 July will mark 70 years since the NHS was founded. Those who remember a time when it didn’t exist know just how precious a creation it really is. As this winter crisis deepens, it is clear that hard and destructive Brexit is not a panacea for the NHS, but the greatest threat it has ever faced.

Dr Paul Williams is Member of Parliament for Stockton South and a member of the Health Select Committee. He is a leading supporter of Open Britain