The NHS is asking for an additional £8bn by 2020 to implement a radical plan, including switching funding from hospitals into other services including GP surgeries, which bosses say is vital to ensure the service can safeguard its future.

NHS bosses warn the Westminster parties to accept the need for the service’s funding to increase from just under £100bn this year to around £120bn by the end of the next parliament – an extra £8bn on top of planned increases in line with inflation – or risk patients suffering “severe” consequences.

The challenge comes in an unprecedented blueprint, drawn up by NHS England chief executive Simon Stevens and published today, which details the far-reaching overhaul the service will push through between 2015 and 2020 in order to relieve pressure on hospitals and GP practices and give patients better care.

The NHS Five Year Forward View envisages GP surgeries becoming like mini-hospitals, with patients able to have a CT or MRI scan or undergo minor surgery, as many traditional hospital services start being delivered elsewhere. The overhaul is also likely to lead to some hospitals offering fewer acute services and instead concentrating on outpatient clinics, diagnostic tests and other non-urgent care.

It also contains proposals for:

• An all-out assault on chronic public health problems such as obesity, smoking and alcohol misuse.

• A major shift of NHS funding away from hospitals into out of hospital services, including GP surgeries.

• Urgent and emergency care services such as A&E, out of hours GP services and the NHS 111 advice line, to work more smoothly together.

• Employers to offer staff cash incentives or vouchers in return for healthier lifestyles, such as losing weight.

• Hospitals to employ GPs, which is currently not allowed.

The NHS has undergone significant improvements in recent years and coped remarkably well with its biggest-ever budget squeeze, said Stevens. “But the NHS is now at a crossroads. As a country we need to decide which way to go.”

With the election less than seven months away and the NHS set to be a key issue, Stevens raised the stakes by warning bluntly that NHS services would deteriorate unless ministers provide the £8bn.

Otherwise patients will bear the brunt, said Stevens. “We have no choice but to do this. If we do it a better NHS is possible, if we don’t the consequences for patients will be severe”, he added.

Seeking to dispel the gloom surrounding the service’s future, which has seen thinktanks, the former Labour health minister Lord Warner and some doctors argue that charging patients for access to services or greater rationing of treatment will become necessary to balance the books, Stevens added: “It is perfectly possible to improve and sustain the NHS over the next five years in a way that the public and patients want. But to secure the future that we know is possible, the NHS needs to change substantially, and we need the support of future governments and other partners to do so.”

His intervention in the intense debate about the NHS’s future could force Labour, the Conservatives and the Liberal Democrats to rethink funding commitments set out over the past month, as he is seeking more money than any of them has promised.

The document, which has been backed by the five other major NHS organisations, calls for whichever party forms the next government to end the ringfence around NHS spending, which has delivered inflation-proof increases since 2010, around £2bn-£3bn a year, and give the NHS a minimum of £1.5bn extra a year during the next five-year parliament.

Dr David Bennett, the chief executive of Monitor, the NHS’s economic regulator, said a real-terms increase equivalent to 1.5% of the service’s budget was necessary to produce “an NHS that really is fit for the 21st century”.

The cumulative effect of the NHS receiving inflation-proof rises plus the extra 1.5% a year to cope with the ageing and growing population, would see its budget come close to £120bn.

But the NHS bosses also want ministers to provide further additional cash for a “change fund”, at an estimated £1bn a year over the parliament, to keep hospital services running smoothly while new services are set up in local communities to provide care that is more convenient for patients and helps the ill avoid unnecessary stays in hospital.

The extra funding would be “investment to lubricate these changes [envisaged]”, added Stevens. Failure to make the extra funding available would make it impossible to improve the early diagnosis of cancer and save the hoped-for 8,000 lives a year – a key government target – or provide some new cancer treatments.

The report says that if rising demand for healthcare can be checked through helping patients stay healthier and out of hospital, and public health measures reduce lifestyle-related illness, the NHS can bridge the expected £30bn gap in its finances by 2020/21 through a combination of 2%-3% annual productivity gains, better care for patients – and the extra £8bn from the government.

The 39-page document “should set the agenda for the next parliament” and “throws down the gauntlet to the political parties to back fundamental changes to health services that could significantly improve care for patients”, said Professor Chris Ham, chief executive of the King’s Fund health think-tank and an ex-coalition Downing Street adviser on the NHS.

Last night all three parties claimed that the blueprint endorsed key planks of their own health policies.

Labour’s Andy Burnham, the shadow health secretary, said the review shows that the Tories’s NHS spending plans – continuing the ringfence, but with no extra money – “would leave a large funding gap and would not be enough to prevent an NHS crisis in the next parliament.” David Cameron was refusing to pledge to match Labour’s promised £2.5bn a year extra funding for the NHS, added Burnham. Labour will not provide the full £2.5bn until 2017-18, however.

Norman Lamb, the Lib Dem health minister, said Labour’s record on private finance initiative-funded hospitals, on the NHS in Wales and refusal to ringfence NHS spending in this parliament showed it could not be trusted over NHS finances. “The Conservatives are not promising anything more than protecting the NHS budget in real terms. If that’s the deal, the NHS would crash. Only the Liberal Democrats are calling for more funding next year and at least one billion more in each year after that”, Lamb said.

Jeremy Hunt, the health secretary, said: “We welcome this important report, which demonstrates conclusively that the NHS has improved dramatically in recent years and can do so in the future, but only if it continues to implement important reforms and is supported by a strong economy.” The government plans to “respond substantively to the Forward View in due course”, sources close to Hunt said.