The true number of job vacancies in Northern Ireland's health system could be nearly double the number reported this week, a union has said.
Valerie Watts, the chief executive of the Health and Social Care Board (HSCB), said on Wednesday that about 1,800 posts needed to be filled.
However, the board has since confirmed that this number did not relate to all health and social care staff groups, and the total could in fact be up to 3,500.
Ms Watts and other health officials had been giving evidence at Westminster to the Northern Ireland Affairs Committee.
A board spokesperson said yesterday: "We have contacted the Northern Ireland Affairs Committee to let them know we will be providing updated figures on staff vacancies. Amended figures will then be reflected in the committee transcript."
Unite lead officer for health Kevin McAdam welcomed the confirmation and called for urgent action to address the threat posed to patient safety.
"The CEO of the Health and Social Care Board provided a figure of 1,800 for the total number of vacancies in the NHS in Northern Ireland.
"Unite was at the forefront of efforts to point out that this figure could be as high as 3,500.
"This belated admission by the board is welcome and perhaps reflects a recognition of the true scale of the problems we face."
Mr McAdam said there was a need for "a reality check" in health.
"Northern Ireland received funding of over £300m for a restructuring of pay scales and improvements to poverty pay that would go a long way to addressing the recruitment and retention difficulties faced by the service," he added.
"Unfortunately, the department continues to use the absence of a locally accountable health minister to justify the delay in entering meaningful negotiations about how this new money can be used to modernise our health service, bring it in line with the rest of the UK and make the health service in Northern Ireland an employer of choice and one that can deliver the healthcare the public here deserve.
"The agenda for change system is the terms and conditions policy of the health system for all parts of the UK.
"It has undergone extensive modernisation agreed across the other three nations, but remains deadlocked in Northern Ireland.
"To properly address this problem, we need the department to engage with employers and trade unions to reach agreement on a way forward."
Last month, the Belfast Telegraph reported how nearly £430,000 a day was spent on hiring agency staff to plug holes in Northern Ireland's health service.