The Irish Nurses and Midwives Organisation has said that most acute hospitals are short between 80-100 nurses.
Speaking at the opening of the union's annual conference in Killarney, General Secretary Liam Doran said that the INMO has had to seek bed closures where there are unsafe staffing levels.
He also said that the INMO has been counting trolley numbers for 12 years and that this was an indictment of successive governments and Irish society.
Mr Doran said the Fine Gael-Fianna Fáil deal in relation to health as "completely minimalist" and completely inadequate.
He described it as health light - "light on reform and light on real change".
Around 350 delegates are attending the three-day conference in Killarney where around 70 motions will be debated.
The main issues are pay restoration, nurses seeking reduced working hours to a 37-hour week and the recruitment and retention of nurses and midwives.
INMO President Claire Mahon said the organisation is continuing to try to ensure that the recent emergency department agreement is implemented by all parties.
Speaking on RTÉ's Morning Ireland, she said, however, that it was not a substitute for the additional beds required within the system.
About 1,500 beds are needed in the acute system and about 2,000 beds are needed in long-term care in order to deal with the demand of the country's ageing population, she added.
She said there is a crisis in emergency departments and also a crisis with the recruitment and retention of nurses within the Irish healthcare service.
Nurses are "fed up of pay cuts, long working hours, excessive workloads and government and management that are not taking the problem seriously," she said.
€10m HSE deal with nurses being paid
The Health Service Executive has said that the €10 million deal reached with nurses before the General Election to avert strikes in hospital emergency departments is being paid.
But it said that the money will form part of its overall deficit for this year.
The €10m deal covered extra leave, promotional posts in emergency departments, as well as an educational bursary for nurses who remain in their posts for a year.
In a covering note to its national service plan at the start of the year, the HSE warned that the overspend this year could reach €500m.
For the first quarter of the year, the HSE ran over budget by around €60m.
Based on the current trend, the overspend by the end of the year is heading towards an estimated €240-€300m.