Trade union leaders have warned the Government that the National Minimum Wage Bill is inadequate to meet the needs of the low paid.
They have criticised the proposed rate of £4.40p an hour and the fact that the Government is reserving the right to review the rate, rather than have an automatic escalator mechanism.
The Irish National Organisation of the Unemployed has welcomed the measure, but its spokesman on jobs, Mr Tony Monks, said it should have been accompanied by measures in the December Budget to take the low paid out of the tax net.
He also criticised the £4.40p rate as "out of date".
SIPTU president Mr Des Geraghty welcomed the minimum wage in principle but said it must be introduced at the rate of £5 an hour to have any significant impact.
He said SIPTU was also unhappy that there was no automatic mechanism to adjust the rate in line with average earnings.
"Any new order in future would ultimately be at the sole discretion of the Minister," he said.
MANDATE, the other union representing large numbers of low-paid workers, has said it would be seeking a rate of "over £5 an hour" through talks on a successor to Partnership 2000.
Its national industrial officer, Mr John Douglas, said anything less than £5 "is totally unrealistic in the context of today's labour market".
Projections by the Economic and Social Research Institute suggest that a minimum pay rate of £4.40p an hour will benefit 13.5 per cent of the workforce and add 1.6 per cent to the national pay bill.
A rate of £5 an hour would benefit 21 per cent of workers and add more than 3 per cent to the pay bill.
While the Small Firms' Association and the Irish Business and Employers' Confederation have accepted the national minimum wage of £4.40p in principle, they are concerned at its impact on labour-intensive firms.
The ESRI predicts 15,000 jobs could be lost in the first year of the new law's operation alone.
However, unions argue that in the current tight labour market, this will not adversely affect overall employment rates.
Many firms are unaware of the Bill's main provisions, although these have been well publicised over the past year.
A recent survey by the Chambers of Commerce of Ireland shows that fewer than 2 per cent of firms are familiar with all main provisions of the measure.