The Irish Medical Organisation has said the failure of the Health Service Executive to agree to sanctions for hospitals that continue to force junior doctors to work long hours was one of the reasons why talks between the two sides broke down.
Junior doctors will hold a one-day strike next Tuesday in protest at the length of their working hours.
Last night, it emerged that in its proposed agreement to the IMO, the HSE promised a maximum of 24-hour shifts by 30 November, other than in exceptional circumstances, with full implementation by 14 January next year.
It also promised full compliance with the European Working Time Directive of a 48-hour week by the end of December next year.
The IMO had sought a sanction of granting extra paid leave to junior doctors if hospitals failed to end shifts over 24 hours.
IMO Senior Industrial Relations Executive Val Moran said this remained one of the main sticking points.
He said: "There are significant differences between the sides still.
"The main issue between the sides is the issue of sanctions. We've sought that if hospitals fail to meet agreed deadlines that sanctions will apply to them.
"The HSE is refusing to apply them in those circumstances."
Mr Moran disputed HSE figures of an average working week of 54 hours for junior doctors, saying it was 63 hours.
He acknowledged that it would be difficult for smaller hospitals to cut working hours and said the IMO had built in measures to allow for this.
Mr Moran outlined the IMO position, saying the deadline for a maximum shift of 24 hours is in January.
He said: "If that deadline is not met - and that's the outer deadline for the worst affected hospitals, the HSE have agreed to that - there would be a sanction applied to those hospitals who do not meet that deadline.
"The HSE have refused point blank to put in a sanction into the agreement. What we're saying is 'if you are saying this plan is credible and is going to be effective, you will not have to pay out a single penny, so therefore why not put in those sanctions?'"
Mr Moran said the sanction would apply to those hours worked above 24 hours. The IMO is suggesting an additional standard rate payment or time in lieu.
He said emergency services would not be affected by the strike action.
The HSE has said there will be no need to sanction hospitals over the European Working Time Directive for junior doctors as there will be an "accountable chain of command" in place to oversee its implementation.
HSE National Director of Industrial Relations Barry O'Brien rejected claims that "significant differences" remained between the two sides.
Speaking on RTÉ's Morning Ireland, Mr O'Brien said he believed the two sides had been working "collectively" at the Labour Relations Commission until the IMO had introduced the issue of sanctions "late in the day".