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Shadow chancellor John McDonnell (L) and Labour’s shadow health secretary Jonathan Ashworth (R) will announce Labour’s NHS spending plan in London today. Photograph: Tolga Akmen/AFP via Getty Images

Labour is to unveil a “rescue plan” for the NHS in England with an extra £26bn of funding a year paid for by higher taxes on companies and the wealthiest in society, as the party puts the health service at the heart of its election offer to voters.

The party’s pledge would give the health service £5.5bn more a year by 2023-24 than the £20.5bn the Conservatives have promised and represent the biggest boost to health spending since Labour was last in power between 1997 and 2010.

It puts pressure on Boris Johnson to increase the money he is committing to the NHS, which he has made one of his three “people’s priorities” and sought to make a Tory vote-winner.

John McDonnell, the shadow chancellor, will say that “proper funding” is needed to maintain a world-class health service as he proposes a 4.3% annual rise in funding.

Labour says the sums it is pledging would end the lengthening delays faced by patients for A&E care, cancer treatment and planned operations, tackle the NHS’s worsening staffing crisis, restore bursaries for student nurses, improve mental healthcare, let hospitals buy scores of new CT and MRI scanners and pay for a new generation of hospitals, GP surgeries and mental health facilities.