Leaders of England's state-funded National Health Service (NHS) warned on Thursday that billions of pounds in extra funds were needed to maintain patient care, laying down the gauntlet to politicians ahead of May's general election.

A new analysis by NHS bodies set out plans for major savings over the next five years by changing the way they operate, such as focusing on public health issues such as obesity and smoking, and reorganising local care.

But it warned these changes would not close a predicted £30 billion ($48 billion, 38 billion euros) funding shortfall by 2020, saying that central government must increase the money it provides by another 1.5 percent a year above inflation—about £8 billion a year.

"Healthcare in this country has improved dramatically over recent years and has weathered recent financial storms with remarkable resilience," said NHS England's chief executive, Simon Stevens, at the launch of the report.

But he warned: "The NHS is now at a crossroads—as a country we need to decide which way to go."

Stevens, who took over earlier this year, later told BBC radio that extra government funding was "perfectly feasible as the economy improves".

The NHS in England had a budget of £95.6 billion last year. The proposed increase goes well beyond what either Prime Minister David Cameron's Conservative party or the opposition Labour party have promised they will provide if they win next May's general election.

Chris Ham, of health charity The King's Fund, said must respond to the appeal for more funding.

"Even if the very challenging estimates for productivity improvements outlined here can be achieved, an additional £8 billion a year in funding would be needed by 2020," he said.

"With the national leaders of the NHS speaking with one voice on this issue, politicians now need to explain whether and how they will find this money."

Created in 1948 after World War II, the NHS paid for through taxation and provides universal healthcare free at the point of delivery.

But the world's fourth-largest employer is coming under severe pressure from a growing population and increasingly expensive treatments, at a time when government spending across the board is being cut.

Cameron's coalition has protected the NHS budget from austerity measures and the has vowed to do the same between 2015 and 2020 if he wins the next general election.

Meanwhile Labour has promised an extra £2.5 billion a year for the NHS.