Sick leave entitlements for public servants are being halved as the Government drives down the 500 million euro-a-year bill for absenteeism.
The new rules, which do not effect teachers, will see the number of days workers can take without a doctor's note fall from seven in one year to seven over two years.
Brendan Howlin, minister for public expenditure and reform, said the restrictions were about striking a balance.
"The reformed arrangements will result in increased productivity, reductions in absenteeism and a significant reduction in the cost of sick leave in the public service," he said. "For most employees the new arrangements will mean that the amount of paid sick leave which they may be granted will be halved."
Mr Howlin said anyone who was genuinely and seriously ill should be given reasonable protection by employers. The Government has set a target of saving 25 million euro off the sick pay bill in this year alone. Information supplied to the Public Accounts Committee in February showed a sick leave bill of 488 million euro for certified time off and 63 million euro for uncertified.
Following a Labour Court adjudication on the reform - opposed by the Public Services Committee of Congress - the big changes will see acceptable uncertified sick leave drop from seven working days in 12 months to the same over 24 months.
Mr Howlin's department is working to have this system in force by September. For workers who fall ill and are signed off by a doctor, their salary scale halves from six months full pay followed by six months half pay, to three months full and three months half.
The six months full-half salary system was originally followed by pension rate of pay for an unspecified length of time. That will be changed to 18 months of so-called temporary rehabilitation pay - equivalent to social protection rates - after the three month full-half salary period.
If a worker suffers critical illness such as a heart attack, cancer, serious accident injury, they will be signed off for six months full pay and six months half pay. All changes to the certified sick leave pay system are expected to come into force in January 2014.
Later, junior minister Brian Hayes said workers who are absent for longer than they are entitled to will not be paid for the days in question. He described the move as "radical public sector reform". But while he insisted the changes will make significant savings for the Exchequer, he was unable to estimate how much exactly could be shaved off the bill. "The current bill at 0.5 billion euro was totally unsustainable," Mr Hayes said. "These reforms will make substantial savings - not just in terms of cash but in terms of efficiency and productivity. It's difficult to say total cost savings."