Patient care is being risked by hospital bosses sending medical notes abroad to be typed up, a union says.
The NHS deficit tops £500m
Public sector union Unison said record-keeping was being outsourced to workers in India, South Africa and the Philippines to help save money.
But Unison warned mistakes had been made in typing up audio files dictated by hospital doctors, which could risk patient lives.
The government urged staff to alert NHS trusts if errors were being made.
MOST COMMON ERRORS
Hypertension (high blood pressure) mixed-up with hypotension (low blood pressure)
Urological (urinary tract) used instead of the word for the nervous system, neurological
Below knee amputation referred to as a baloney amputation
Dosages mixed up with number such as 15 transcribed as 50
Unison, which represents nurses and non-clinical staff such as medical secretaries, highlighted a series of common blunders, including the word hypertension (high blood pressure) instead of hypotension (low blood pressure).
Urological was also mixed up with neurological, while mistakes were made with dosage figures.
The union said, when recordings were not clear, hospital-based medical secretaries could check with the doctors.
But they warned that when the service was outsourced this was not possible.
It also said the secretaries often knew something about a patient's medical history.
Unison general secretary Dave Prentis said: "Lives are being put at risk by hospitals desperate to save money.
"Patients' medical records must be absolutely up-to-date and accurate.
"The consequences of typing errors are too frightening to contemplate.
"The government has to rethink this latest idea that medical typing can be done at a distance without risking patient health.
"It is ridiculous and is a step too far."
Companies are thought to be approaching trusts, saying outsourcing medical secretary work will be a way of saving money.
Several pilots are under way in London, Norfolk, Wiltshire, Cornwall and Bedfordshire.
The NHS is facing a £512m deficit with nearly a third of NHS organisations failing to balance its books last year.
Over 30,000 medical secretaries are employed by the NHS to keep medical records up to date.
It is not known how many have been laid off in the recent wave of job cuts - over 12,000 post closures have been announced since the beginning of the year.
But Unison fears the trials will become permanent arrangements and lead to secretaries losing their jobs.
The Department of Health said it had confidence in NHS trusts over medical records.
But a spokeswoman added: "If Unison has concerns that incidents affecting patient safety have not been acted upon, then we urge them to share this information with the NHS trusts concerned so that they can investigate them."
Shadow Health Secretary Andrew Lansley said: "It is deeply concerning that life-threatening mistakes are being made in an effort to cut costs.
"Standards should be maintained irrespective of provider and should not be compromised for short-term cost cutting measures."