The number of NHS patients having surgery in private hospitals has nearly trebled since 2010, sparking accusations that for-profit companies are benefitting from an “enfeebled” health system under the Conservatives.

NHS figures obtained by the Guardian show that it paid for 214,967 people in England to have an operation in a private hospital in 2009-10, Labour’s last year in power. The figure soared to 613,833 last year, a 185% rise in nine years.

The figures come as NHS trusts are increasingly forced to send patients to for private surgery because they are too busy and understaffed to do the operations themselves. The sharp rise in outsourcing has coincided with the waiting-list for non-urgent operations ballooning to 4.6m, the highest figure since records began in 2007.

The privatisation of healthcare has emerged as a key issue in the general election campaign. Labour allege that Boris Johnson will sell large parts of the NHS to private US health firms as part of a post-Brexit trade deal with Washington. The party also says the NHS’s annual drugs bill could soar from £18bn to £45bn if US pharmaceutical firms are given freer access to the British market. The prime minister has dismissed the claims.

Trusts are striking deals with independent providers to carry out surgery, including cataract removals and hip and knee replacements, and also some non-surgical treatments, including for cancer.

King’s College hospital trust in London, for example, sent 216 patients to BMI Healthcare in February and March, either to have surgery or undergo an endoscopy, to help cut its waiting list. It also sent 10 patients to undergo bariatric surgery at the Princess Grace private hospital in central London, and paid £1.3m to 18WeeksSupport to treat patients with eye problems whom it could not deal with fast enough itself.

“A decade of cutting over 15,000 beds and failures to recruit staff under the Tories is forcing more and more patients out of the public NHS into poor quality private hospitals,” said the shadow health secretary, Jonathan Ashworth.

“The failing health secretary has allowed waiting lists to balloon with patients left in pain and distress. A bonanza for the private sector is the consequence exposing Mr Hancock’s famous claim of ‘no privatisation on his watch’ as utterly hollow,” he added, referring to comments Matt Hancock made to MPs in January.

The 613,833 NHS-funded procedures last year were undertaken at 296 different private hospitals by 144 separate providers. BMI Healthcare treated 115,925 patients, the highest number, at its hospitals. Spire hospitals performed 80,095 procedures and Circle Health 41,435.

Dr Tony O’Sullivan, a retired paediatrician and co-chair of the campaign group Keep Our NHS Public, said: “These are totally shocking figures that provide hard evidence that the NHS has been enfeebled after close to a decade of Conservative government and been left desperately short of staff and money.”

The Guardian disclosed in July that private firms were given a record £9.18bn of the NHS budget in 2018-19, up from £8.07bn in 2014-15.

In another illustration of outsourcing, Northumbria Healthcare trust has agreed to send between 120 and 150 people with cancer a year for oncology treatment at the private Rutherford Cancer Centre.

The organisation representing independent providers of NHS care defended their role and said their involvement meant patients were able to avoid spending a long time waiting for the NHS to treat them.

“While there’s been a growth in the use of private provision in the NHS, this still equates to just 7% of the NHS budget, and the recent slowdown in work going into the private sector has coincided with a period where NHS waiting lists have increased substantially”, said David Hare, the chief executive of the Independent Healthcare Providers Network.

“The reality is that without private provision of NHS services patients would wait far longer for their care and have less choice, which is why the public repeatedly report being relaxed over who provides their NHS care providing it is high quality and remains free at the point of use.”

The shadow chancellor, John McDonnell, pledged last week that a Labour government would get rid of all privatisation in the NHS by it taking contracts back in-house as they come to an end. “We believe actually we shouldn’t be allowing people to profiteer from the NHS. The general public feel as though we shouldn’t be pouring money into the pockets of profiteers”, he told the BBC’s Andrew Marr Show.

In a statement, a Conservative spokesperson said: “In the face of rising demand, the NHS is treating more people than ever. There are 2.4m more operations happening every year, compared to 2010. We have committed to the largest financial settlement in NHS history, backing it with an extra £33.9bn in cash a year by 2023/24.”

Meanwhile, the Tories have pledged to increase the number of GPs in England by 6,000 by 2025 and offer patients 50m more appointments if they form the next government. Half of the extra family doctors would come from expanding training places and half from better retention and also recruiting GPs from overseas.

But Labour scorned the announcement. Ashworth said: “[In 2015] Tory ministers promised us 5,000 extra GPs but in fact we have lost 1,600 GPs under the Tories.”