The Care Quality Commission (CQC) has recommended that Colchester Hospital University NHS Foundation Trust be put into special measures.
Professor Sir Mike Richards, national clinical director for cancer and end of life care, has called for the change after a CQC inspection found badly recorded data and potentially poor choices in terms of treatment programmes for patients.
Concerns raised by Professor Sir Mike and the CQC have now been passed on to Monitor, a sectoral regulator for health services across England.
After an inspection, CQC investigators found that the number of cancer patients that suffered undue delays in treatment were not properly recorded and this may have been part of a sustained effort to cover up bad management practices.
So serious were the CQC's findings that Essex Police force have been brought in to the inquiry to see if any managers, doctors or nurses might be criminally liable for their part in the altering of data.
To mark the start of the investigation, Colchester Hospital University NHS Foundation Trust has been told to write to 30 patients, or their next of kin where this is not possible, offering for a treatment review to ensure proper levels of care.
Professor Sir Mike stated: "If you are diagnosed with cancer - you are entitled to think that your hospital will do all they can to ensure you get treatment you need as soon as possible.
"It is shocking to think that people's lives may have been put at risk for the sake of the waiting time figures. It is essential that people in north Essex can have confidence in their hospital."
Adam Cayley, regional director for Monitor, which will make any final decision regarding the move into special measures, said it has opened a formal investigation into whether licence conditions were breached.
This is especially important given the trust's foundation status, which awards it greater funding and staffing over other smaller units.By Chris Stevenson