If automatic enrolment in pensions is not handled correctly then our entire pensions framework is under threat, businesses have told an Oireachtas committee.
Business owners also warned against changes that could force employers "to level down their existing provision".
The Joint Committee on Social Protection is examining the bill which will introduce auto enrolment (AE) for pensions.
It heard that Ireland is the only Organisation for Economic Co-operation and Development (OECD) country that does not operate an AE or similar system.
The Irish Business and Employers Confederation (IBEC) expressed serious concerns about the current bill, while maintaining that it is a "strong advocate" for AE.
Fergal O'Brien, executive director of lobbying and influence, said that having no waiting period for AE could introduce "anomalies and confusion" which he claimed could "undermine existing occupational pension provisions".
The current system of occupational pensions is delivering, he said, and urged that we "don't break that element which is working effectively".
He strongly cautioned against introducing "any uncertainty", pointing out that the current system works "on trust".
"If we break that trust, then I think our entire pensions framework is under threat", he warned.
Mr O'Brien listed "some" of the changes that IBEC wants to see introduced.
It wants the upper salary threshold for inclusion in the AE scheme to be nearly halved, from €80k to €50k.
Self-employed people should be included, he said.
Workers who leave the AE scheme should be automatically re-enrolled after three years, and not two as is currently proposed, which he warned this impose too great an administrative cost on employers.
"We are concerned about the scale of contributions required for both employees and employers", Mr O'Brien said.
He urged that "competitiveness and affordability reviews are completed before each stage of the contribution increases are progressed".
"Contribution costs will present a significant affordability challenge for many workers, particularly as they continue to struggle with cost-of-living challenges", he said.
"Employers and our members have been faced a raft of State- and market-related labour-cost increases in recent years, and we are concerned that contribution increases will add further to the very serious competitiveness risks facing Irish business."