I am a GP in Tower Hamlets, east London. Our centre is a stone's throw from the Olympic Park in Stratford. After the greatest show on earth left town, life here quickly returned to normal – Tower Hamlets is one of the most deprived boroughs in the country. Just before the Olympics, an eight-year-old boy came to see me. He was taking part in the opening ceremony and had developed a pain in his foot brought on by intense rehearsals. As I sat down to watch the ceremony, I kept an eye out for my young patient. Like thousands of NHS staff, I felt very proud that Danny Boyle's extravaganza celebrated the NHS as a singular achievement in universal, free healthcare.

The Bromley by Bow Centre, where I work, is renowned as a model of holistic healthcare and is funded by the NHS and the voluntary and private sectors. You could even argue that it is a microcosm of what David Cameron's Big Society might look like. Andrew Lansley gave his first speech as health secretary here.

The Downing Street rose garden press conference and honeymoon period of the coalition now seem a long time ago. The 2010 Conservative manifesto promised to stop "the top-down reconfigurations of NHS services, imposed from Whitehall" but, only weeks into government, the mother of all reconfigurations was unveiled.

I watched aghast at the slow-motion car crash of the health and social care bill during its turbulent passage through parliament and thought of its affect on the many deprived patients I have in my care.

The act comes into effect on Monday. Very few people understand its implications but it will affect each of us arguably more than any other legislation passed in our lifetimes.

It is the final stage in the systematic dismantling of the NHS – a process that began about 25 years ago – carried out by stealth.

The government's case for change largely rests on the premise of the NHS no longer being affordable, particularly in the current climate, and that it needs to be modernised. While there is evidently room for improvement, research overwhelmingly shows that the NHS performs well compared to other healthcare systems internationally, is cost-effective and rated highly by patients.

The Health and Social Care Act 2012 is virtually impenetrable but the main thrust of it is: primary care trusts and strategic health authorities will be disbanded. In their place, clinical commissioning groups – also known as GP consortia – will control about £60bn of the NHS budget and commission local services. Commissioning will take place through competitive tendering. NHS contracts will be opened to the voluntary and private sectors. Already, £250m of NHS services have been forced open, with 105 private firms granted contracts. This year, a further £750m of services will be tendered. The NHS annual budget is more than £100bn – there are huge profits to be made for private healthcare companies.

The NHS, as we know it, will effectively be abolished just short of its 65th birthday.

The government claims private providers will improve standards through competition and choice. The experience of the NHS with the private sector so far – whether through private finance initiative (PFI) hospitals, treatment centres or the corporate takeover of out of hours care – has been disastrous. The marketisation of the NHS has driven up costs and produced worse results. The track records of some private providers now entering the NHS, such as UnitedHealth Group, are not impressive.

GPs, such as myself, are meant to be at the heart of running the new NHS but only a small number will be involved. This is why corporates such as UnitedHealth are preparing to take over the complex task of commissioning.

Competitive tendering fragments healthcare. Patients with chronic diseases will be looked after by multiple providers. This will particularly apply in Tower Hamlets, where chronic diseases such as diabetes are more prevalent. I have in mind a particular patient who needs to be seen for eye-screening and attend hospital clinics for checks to his feet and for lifestyle education. Right now most of that would be under the NHS but in future he will have those things provided separately by several different providers, making it difficult to coordinate.

Private providers will also "cherry-pick"; taking away income from NHS providers and leaving the NHS with expensive, risky healthcare.

The Health and Social Care Act effectively legislates against free, universal, comprehensive healthcare. Yet this legislation is just one of many planks in the dismantling of the NHS. We now know that more than 20 NHS trusts, comprising about 60 hospitals, are at risk of going bust. This is, in large part, due to the financing of extortionate PFI debts projected to rise above £79bn despite the original cost of the hospitals being around £11bn. The rapid restructuring of South London Healthcare Trust, with the downgrading of neighbouring, solvent Lewisham hospital, is a template that can be used across the country. No hospital is safe from closure.

The government consistently claims the NHS budget is protected. In reality, the NHS is being forced to make cuts dressed up as efficiency savings of £15bn-£20bn by 2015. Across the country, A&Es, maternity and other services are being closed, with thousands of jobs lost. Patients with chronic and complex diseases will continue to lose services essential for their care. In north-west London, four A&Es have been downgraded, with none for the boroughs of Hammersmith & Fulham, Ealing and Brent – a population of 750,000 or a city the size of Leeds. As a result of these changes, people will die.

Once you combine the consequences of the Health and Social Care Act with PFI debts, NHS trusts going bust, efficiency savings and cherry-picking, the NHS withers away. Rationing of care will become more widespread until we have a two-tier system in which the haves will take out private insurance and the have-nots will be looked after by a third-class health service.

We know that health is inversely related to socioeconomic status. With the greatest chronic disease burden, those who are deprived, like our patients in Tower Hamlets, will thus be most affected. I'm thinking of several patients of mine with multiple conditions who would not be able to afford private health insurance and would therefore rely on a severely depleted NHS.

When the eight-year-old boy who came to see me is an old man, there may not be an NHS to look after him. Aneurin Bevan was once asked how long the NHS would survive. He replied: "As long as there are folk left with the faith to fight for it." This is why local NHS campaigns are joining up to fight back. The government and other vested interests may think the battle is over but this is just the start of the struggle to take back our NHS.