Cancer sufferers are being put at risk and care for patients undergoing surgery is “severely compromised” as a result of constant staff shortages on wards, according to devastating first-hand testimony from inside the NHS.

An astonishing dossier of concerns raised by nurses about the impact of staffing levels on patients reveals that nurses with the right skills are often in short supply, full staffing levels are becoming a “rare event”, and some emergency patients are being sent home as a result.

The testimony, compiled from 18,000 anonymous submissions from hospital nurses and shared with the Observer, states that some nurses are being asked to complete procedures beyond their expertise, while many vulnerable patients are not being given the emotional support they need. Some experienced nurses say they believe they are seeing the worst shortages in decades.

Compiled by the Royal College of Nursing, the dossier reveals the severe concerns over patient safety. One nurse writes: “A lack of trained chemotherapy nurses means we are treating patients every day in an unsafe manner, mistakes are being made and management have no answers to the staffing crisis.”

Another states: “Our [cancer] patients may have to have less psychological support as we do not have the time to sit with them and reassure them. It may also mean that timely chemotherapy delivery is difficult. Today’s shift, where we were fully staffed with the majority of our own team, was a very rare event.”

There were similar concerns in relation to patients heading for surgery. “The level of [nursing] staff running theatre lists daily is inadequate,” one nurse states. “We are operating with the worst levels in theatre that I have seen in 40-plus years in theatres. Patient care is severely compromised due to staffing levels.”

Another writes: “Many times I have felt unsafe and when escalated have been told ‘but nothing major happened’, meaning the ‘what ifs’ are never addressed until something happens. The skill-set of nurses is a major problem, with nurses having to scrub for cases out of their competency through sheer lack of numbers.”

Meanwhile, an A&E nurse reveals: “Due to staffing issues some emergency triage patients are sent home, if they are clinically stable, to return again the next day to be treated.”

There are also serious complaints about the level of provision of psychiatric nurses. “One community psychiatric nurse for half a county for a whole day is not a safe staffing level,” writes one nurse. “Staffing levels and high staff turnovers are a huge problem … that needs addressing before anyone else is harmed.”

A recent report by Macmillan Cancer Support found that there were widespread shortages of specialist cancer nurses. Hospitals in England were found to have vacancies for more than 400 specialist cancer nurses, chemotherapy nurses, palliative care nurses and also cancer support workers.

The disclosures come as the Royal College of Nursing calls for new English laws to make ministers accountable for ensuring safe staffing levels. In 2016 Wales became the first country in Europe to introduce safe staffing laws for nursing, while Nicola Sturgeon, the first minister, has promised legislation in Scotland.

In her speech to the college’s annual congress on Sunday its general secretary, Janet Davies, will say that nurse recruitment and morale have been plunged into crisis by “workforce planning driven by finance and not the needs of patients. The care we are able to provide is totally compromised by short staffing, and we cannot repeat this often enough: mortality levels increase when the level of registered nurses falls. We know our patient outcomes are better when there are more nurses to care for them.”

A Department of Health and Social Care spokeswoman said that overall staffing levels in the NHS were at a peak. “The NHS would collapse without our wonderful nurses – the fact that the NHS is ranked as the safest healthcare system in the world is a testament to them,” she said.

“From this year we will train 25% more nurses, we are committed to helping them work more flexibly to improve their work-life balance, and we have awarded a pay rise of between 6.5% and 29% in a deal backed by the Royal College of Nursing themselves.”