NHS patients are recorded as having higher mortality rates than those in almost every other wealthy country, according to a major international analysis, despite record levels of funding.
Britain ranks near the bottom of a league table for so-called treatable mortality - deaths that are considered potentially avoidable with timely and effective healthcare - with only the United States performing worse.
The findings are expected to intensify scrutiny of NHS survival outcomes, waiting times and overall performance, as patients continue to face long delays in diagnosis and treatment.
Health spending has risen by more than £60billion in a decade, reaching £242billion a year, yet the NHS continues to lag behind comparable countries on a range of health indicators.
Experts warned funding has been 'poorly targeted', with more spent on staffing and pay while hospitals face shortages of equipment, scanners and infrastructure.
The UK has 19 MRI, CT and PET scanners per million people, compared with around 50 in similar tax-funded systems and up to 68 in others.
It also has fewer hospital beds than many comparable nations, contributing to longer waiting times and delays in diagnosis and treatment.
These pressures are reflected in international outcome measures, including survival within 30 days of a heart attack, where the UK performs below average.
The findings, reported by the Telegraph, also found Britain is among the worst performers for unmet medical needs, with patients reporting difficulties accessing timely care.
Long NHS waiting lists for specialist appointments and elective surgery remain widespread, with many patients waiting months for treatment.
The Institute for Public Policy Research said years of underinvestment in NHS infrastructure - including hospitals, scanners and technology - are driving these pressures.
Capital investment in the NHS remains around half the level seen in comparable countries.
Despite debate over NHS reform, researchers dismissed a shift to European-style insurance systems as a 'pointless distraction'.
They said the core issue is how NHS funding is allocated and invested, rather than the funding model itself.
Health Secretary Wes Streeting has insisted that NHS budgets must be spent more effectively, adding that ministers face difficult choices and must ensure spending is 'well spent'.
He said: 'This is a timely report, as the arguments against the NHS grow louder.
'It dispels the myth that insurance-based healthcare systems are more efficient. While this Government is cutting the back office to reinvest in the front line, those who would rather move to an insurance system would do precisely the opposite.
'The NHS model is also the fairest way to provide care, rather than allowing your wealth to decide your health. The founding promise of the NHS is just as relevant today as in 1948: that healthcare should be made available to all, so whenever you fall ill, you never have to worry about the bill.'
The IPPR report also highlighted wider concerns around NHS capacity, infrastructure and long-term planning.
Last week, separate NHS England figures showed that some trusts recorded higher-than-expected numbers of deaths compared with statistical expectations.
Blackpool Teaching Hospitals NHS Foundation Trust recorded deaths 31.9 per cent above expected levels.
Medway NHS Foundation Trust recorded deaths 30 per cent above expected levels.
University Hospitals of Morecambe Bay NHS Foundation Trust recorded deaths 28.8 per cent above expected levels.
The NHS stresses that these figures are not a measure of quality of care and should not be interpreted in isolation as evidence of poor performance.
All three trusts are also among lower-ranked NHS organisations in national performance tables, with inspectors previously identifying concerns requiring further review.
