The KwaZulu-Natal Health Department has banned nurses and doctors from moonlighting, saying the practice is being abused.
Two major health workers' unions have rejected the move, saying their members in the public sector are poorly paid and rely on after-hours work to help them make ends meet.
From this month, all health workers employed by the KZN Health Department are prohibited from working outside the public service.
Spokesman Chris Maxon said on Tuesday that it was policy that health workers could not engage in remunerative work while employed by the department.
Exceptions had been made in the past with a number of stipulations, among them that extra work should not be undertaken during working hours and there should be no conflict of interests.
"But there have been instances of abuse of the system and the department head has decided to withdraw the privilege," Maxon said.
According to the circular, signed by department head Sibongile Zungu, all employment outside the public service has been banned "while the department reviews controls and processes".
Nurses union Denosa said that although some staff members might have abused the system, the department should have investigated each case.
"There have been cases, for example, where staff use their days off for extra work and they are tired when they go back to work and book off sick," Denosa said.
"But (abusing the system) should not be dealt with as a blanket ruling. This type of restriction is not fair.
"There is a reason why people do extra work and it is because they need to supplement their income.
"It is the responsibility of managers to ensure the system is not abused.
"All you do is observe and if you pick up a pattern of abuse, you investigate and take action against the individual. You do not just shut (the system) down and deprive others."
Dr Akhtar Hussain, national councillor of the SA Medical Association, said many doctors worked after hours because "they earn peanuts".
"Doctors do not receive livable wages. Senior doctors are unhappy even after the recent occupation specific dispensation (the government's revised salary structure for specific occupations in the public servants) was implemented, as only interns and registrars have properly benefited from it.
"Some senior doctors are now earning less than they were before the occupation specific dispensation was implemented. We obviously do not condone people running private practices and working for the state.
"But the government's poor pay is causing the problem. They need to investigate each case, not punish everyone."