Cancer scans showing the presence or spread of the disease are going unread for as long as six weeks as the impact of the doctors’ pension dispute on patient care worsens.

Hospitals are increasingly having to reduce the services they can provide as thousands of consultants stop doing overtime in order to avoid being hit by unexpected tax bills of up to £80,000.

“Radiology waiting times are unacceptable, with [delays of] five to six weeks for cancer patients on treatment to get a report,” said one consultant quoted in a new dossier of evidence collected by the Hospital Consultants and Specialists Association (HCSA).

A consultant radiologist at another hospital said: “Scan report turnaround time has gone from one week to over a month. Unexpected and critical findings are going unreported for weeks. We are now just firefighting.”

And a cancer specialist at a third hospital said: “There are cases where cancer has been missed as a result [of scans not being read for weeks].”

Patients are turning up for appointments with their specialist but going straight home again because their scan has not been read, rendering the consultation pointless.

The HCSA’s findings are based on reports from 1,116 consultants across the UK. They also reveal that one hospital can no longer treat patients at the weekend who suffer bleeding on the brain with a procedure known as coiling because doctors staffing the service have scaled back their hours as a result of the pension problem.

Patients who turn up in A&E in severe pain from the neurological condition trigeminal neuralgia are having to be admitted and given doses of strong painkillers because surgeons are not available to operate on them.

“The breakdown of hospital services is gathering pace and threatens to run out of control by winter unless the Treasury admits it has got it wrong,” said Dr Claudia Paoloni, the HCSA’s president.

“Across the UK we hear reports of clinics and surgery grinding to a halt due to staff shortages for which doctors cannot be blamed.”

The pensions problem – which can see doctors in effect paying the NHS to work extra shifts – is also prompting growing numbers of consultants to quit the NHS to work abroad.

At one NHS trust in England three of a 30-strong team of anaesthetists are leaving for Australia and New Zealand. In Sussex four senior registrars – who are soon due to become consultants – are taking up new jobs at that level in Canada and the Middle East.

The HCSA’s dossier confirms the picture of widespread and growing cancellations of planned operations, especially sessions of “catch-up” surgery at weekends to help reduce ballooning waiting lists, that the Guardian reported on 8 July.

A hospital in Essex has had to cancel cancer surgery because so many of its anaesthetists have stopped working extra hours so that they do not earn additional income that could then trigger a hefty pension tax bill. Some consultants have had to remortgage their houses to pay the amounts sought by the HMRC.

Clinics and operating theatres in Liverpool that were previously running every weekend are “now at a standstill”, according to the HSCA, which has 3,500 doctors as members.

“For years hospitals have papered over the cracks [of doctor shortages] by cajoling medical staff to work ever more overtime, partly because they know they can exploit doctors’ overriding desire to make people well. This now lies exposed by a tax system which means hospital doctors stepping up to cover gaps in patient care are left facing financial penalties running into tens of thousands of pounds for doing so,” said Paoloni.

The government has tried to tackle the problem by letting consultants pay less into their pension for up to 10 years, in an effort to avoid reaching the £1.1m limit of their pension pot, in what is known as the “50/50” scheme. But the HCSA, British Medical Association and NHS Providers, which represents NHS trusts in England, have all rejected that as inadequate.

The Department of Health and Social Care (DHSC) will examine other possible solutions. The health secretary, Matt Hancock, has promised to fix the problem before the next tax year begins in April 2020.

In a further sign of the worsening impact on NHS services, seven in 10 (71%) consultants said pension issues had directly affected patient care in their hospital. Half (51%) said the problem had forced them to stop doing overtime while 26% had cut the amount of extra work they did.

A DHSC spokesperson said: “We will consult on proposals to make NHS pensions more flexible for senior clinicians, in response to evidence that shows this issue is having a direct impact on retention and frontline service delivery. We will carefully consider all views on our proposals.”