Nurses are set to tell politicians they need to do more to tackle shortages within the profession.
The Royal College of Nursing has over 22,000 members in Wales
Members of the Royal College of Nursing (RCN) will claim there are close to 2,000 nurse vacancies in Wales, not 600 as quoted in official figures.
The body will state these claims in giving evidence to the Welsh assembly's Health and Social Services committee on Wednesday.
The assembly government has said nurse vacancy figures were falling.
Other evidence due to be submitted by the RCN are claims that the cost of filling the gaps by using agency staff has risen by 117% to £21m over three years.
Following a survey of 10,000 members, the RCN found that one in nine nurses is planning to leave the profession soon.
The RCN will call on politicians to tackle recruitment and retention of nurses, as well as other issues which are affecting the nursing profession and patient care.
The RCN says many are planning on leaving the profession
"The aim of individual nurses has always been to improve the health of patients," said Tina Donnelly, the director of RCN Wales.
"We are committed to contributing to the development of Welsh health policy and the evidence we have submitted will focus the committee's attention on the nursing issues that really matter to patients in Wales, so that the patient experience is enhanced."
Filling nursing posts and tempting nurses who have left the profession to return to work has remained a challenge for the NHS in Wales and the Welsh Assembly Government.
A spokesperson for the Welsh Assembly Government said: "While we share the Royal College of Nursing's concern about nursing vacancies, it is nevertheless true to say that the nurse vacancy figure for the whole of Wales is 2.2% and falling.
"This means that 98% of nursing vacancies have been filled here in Wales.
"We agree that the number of agency staff working in the NHS is too high and we aim over time to turn these agency places into nursing positions."