The Mandate Trade Union has warned that employers will use increases in social welfare rates announced in the Budget to avoid raising wages.
General Secretary Gerry Light said Budget 2023 was, like all budgets, a "mixed bag".
He told the Oireachtas Committee on Enterprise, Trade and Employment that he does not think any increases in social welfare supports and State supports are a replacement for decent wages.
Mr Light warned that employers were already suggesting that they could "substitute" these social welfare increases for wage increases.
The committee is examining the minimum wage and cost-of-living crisis.
Mandate represents 27,000 workers, many in the retail sector where pay levels are relatively low.
Mr Light criticised the Government for moving "far too slow" towards introducing a living wage, and urged that this be "urgently" addressed.
The Low Pay Commission has recommended that a living wage of 60% of the median wage of all workers be set in law.
Mr Light said he does not have confidence that the Government will accomplish this, adding that he has seen "no evidence" that it will be introduced.
Pushing for an increase of the minimum wage to €14, Mr Light dismissed "all of the sabre-rattling and the scare-mongering" that raising the minimum wage would cost jobs.
Earlier this month, the Government accepted the recommendation of the Low Pay Commission to increase the National Minimum Wage by 80 cent to €11.30 per hour from 1 January 2023.
Ultan Courtney, Chairperson of the Low Pay Commission, accepted that the increase "is not a panacea" and will not compensate for rising inflation.
While he insisted that it is "significant", he acknowledged that additional supports for low paid workers would be needed.
Mandate dismissed the planned increase as a "grave injustice".
Jonathan Hogan, Assistant General Secretary, said that the "bare minimum" requirement was to match inflation, as "anything less is a wage cut".
Gerry Light dismissed employers' calls for a phased introduction of the increase as "nonsensical".
He also noted that he had served as a Low Pay Commissioner for six years.
Mr Courtney told Sinn Féin Senator Paul Gavan that some people on the minimum wage have told him that they do not want an unsustainable increase in it, something at which the senator expressed surprise.
"Would you consider making a supplemental increase during next year?" Senator Gavan asked, pointing to rampant inflation.
"The commission is not in the job of chasing inflation," Mr Courtney responded.
The recommended increase was based on a 4% inflation rate for next year, the committee heard.
Solidarity-People Before Profit TD Paul Murphy noted that Minister for Finance Paschal Donohoe said inflation is expected to hit 7% in 2023.
While warning of a possible wage-price spiral, Mr Courtney said: "We do fear it - but there's no evidence of it."
He accepted that Deputy Murphy's concerns over a "profit-price spiral", while novel, were deserving of attention.
Paul Murphy said that perhaps there is a need for a "high profit commission" as well as a Low Pay Commission.