Employers are to insist that workers suffering from swine flu produce a medical certificate to prove they are not "faking" their illness, the Sunday Tribune has learned.

The approach has provoked strong criticism by the Irish Medical Organisation (IMO), which warned it could increase the spread of infection by encouraging people to make unnecessary visits to GPs, many of whom could already be under huge strain.

The HSE last month warned businesses to plan for an absenteeism rate of 15% due to the H1N1 pandemic.

But Irish Business and Employers Confederation (Ibec) spokesman Pat Delaney said its members do not want swine flu "turning into a charter for people to stay at home".

While it is "absolutely vital" that no employer allows anyone to come onto the premises who is ill with swine flu, he said a medical certificate would be required to demonstrate illness.

"No employer would want to see their employee suffer from hardship. Once they are certified, a company's normal policies and procedures for illness would apply," Delaney said. "It is very important people get certifiable evidence that they are unable to go to work and that is what certification provides, it says that you must not go to work."

Small Firms Association director Patricia Callan said swine flu could be used as an excuse for absenteeism, with "people who have sniffles saying they have swine flu".

"There is never a situation where a company would want somebody to come in with the ordinary flu. But if you self diagnose and stay away from work, that's not acceptable either."

Dr Ronan Boland, chair of the IMO's GP committee, said absence from the workplace is "primarily an issue for industry".

"If 15% of the workforce turns up at GPs' surgeries solely or predominantly for the purpose of getting an illness cert for their employers, this will not alone be rendering the workload of GPs intolerable but they are also passing on infections to others," he said.

"If the anticipated numbers materialise, it will be neither feasible nor medically advisable to have large numbers turning up for a medical cert."