The NHS is paying private firms record sums to analyse diagnostic scans because hospitals are too busy and understaffed to do the work themselves, research has revealed.

The amount being spent on outsourced the interpretation of CT and MRI scans is “spiralling out of control” and reflects a short-sighted failure to train enough doctors, ministers are being told.

Scans are vital for diagnosing diseases such as cancer and for monitoring patients’ responses to treatment, so they need to be done quickly. Many hospitals, however, rely on non-NHS health companies reading some scans to ensure they get the results promptly.

NHS trusts and health boards across the UK gave £241m to private firms to undertake such work last year. As demand increases, spending has doubled in five years from £120min 2021 and tripled from the £81m spent in 2018.

The figure for 2025 of £241m was £25m or 12% higher than the £216m outsourcing bill a year earlier.

The Royal College of Radiologists (RCR), which collated the figures in its annual workforce census, said health service spending on private scan reading was “ballooning”. The NHS-wide shortage of radiologists has left hospitals with too little capacity to read all scans, meaning the service is “haemorrhaging” cash to independent firms, it said.

The RCR also raised concerns that the analysis done by private firms was sometimes so poor that NHS radiologists had to read scans again, raising questions about the benefit of outsourcing.

Eight-six per cent of NHS radiology department heads had serious concerns that privatisation results in lower-quality reports, and 90% said NHS radiologists needed to double-check outsourced reports.

“Increasing NHS reliance on outsourcing in radiology is not sustainable and the costs of this are spiralling out of control,” said Dr Stephen Harden, the president of the RCR.

“In the short term, outsourcing can help to manage diagnostic backlogs, but it cannot be a long-term solution to workforce shortages. Clinical radiologists play an essential role in making most diagnoses, but rising demand for scans is outstripping our capacity.”

The Department of Health and Social Care (DHSC) acknowledged that radiology services were under growing pressure, but said the forthcoming NHS workforce plan would provide the staff needed.

Harden has urged ministers and NHS chiefs to boost the radiology workforce by creating more training roles in the profession. There are currently 11 applicants for every training post.

“To ignore this call and continue to spend heavily on outsourcing would be short-sighted, would not be the best use of NHS funds and would not be in patients’ best interests,” he said.

The NHS could become permanently reliant on private firms to read scans, the Centre for Health and the Public Interest thinktank said.

Its director, David Rowland, said: “The use of private teleradiology companies to read NHS scans is growing rapidly. History shows that once the government hands these roles over to the private sector, they remain in private hands, taking income and revenue away from NHS hospitals and removing the opportunity to train the next generation of NHS staff.

“The risk is that the NHS becomes wholly dependent on private companies for this critical function, whose sole focus is on the bottom line.”

A DHSC spokesperson said: “We recognise the pressures facing radiology services, and that demand for diagnostic imaging has risen significantly in recent years.

“Despite this, the NHS carried out 30m diagnostic tests in the last year alone, and compared with the previous 12 months, 95,000 more patients were diagnosed with cancer or given the all-clear within 28 days.

“But we know there is more to do, which is why this government will publish a 10-year workforce plan to help deliver a transformed health service in England. This will make sure we have the right staff in the right places, with the right skills to care for patients, when they need it.”