Last month, health chiefs were warned they were relying too heavily on temporary nursing staff provided by agencies, after the annual bill more than doubled in the space of two years to £9.3m.
The Royal College of Nursing (RCN) responded by saying the NHS should invest in permanent staff and stop relying on expensive workers provided by private firms.
However, days later, the NHS posted a notice advertising a contract worth between £10m and £18m over two years, in exchange for the supply of temporary staff, including agency nurses and healthcare assistants to work at health boards across Scotland.
The Government promised the permanent vacancies would be filled and the use of agencies would fall, but said temporary staff could help respond to periods of absence.
However, Jackson Carlaw, health spokesman for the Scottish Conservatives, said the continued use of nurses from external firms was a "horrific waste of money".
"This is the SNP's chaotic approach to forward planning coming home to roost," he added. "Instead of spending the money required to train young nurses, it has splurged tens of millions on expensive agency alternatives. This move suggests that strategy will last for at least another two years."
Multiple companies, who must be registered with the Care Inspectorate, could win deals under the new contract and must submit bids by Saturday. Potential providers have been told their bids will be judged half on the price they offer, with a quarter weighted towards quality assurance and the other quarter judged on contract monitoring.
At the end of March this year, there were 1449 nursing posts, or 2.6 per cent of the total workforce, vacant in Scotland. At the same point in 2012, there were 905 vacancies, although the total nursing workforce has increased over the two years by about 2300.
Meanwhile, between 2011-12 and 2013-14, the amount the NHS spent on agency nursing staff in Scotland annually increased from under £4m to £9.3m. While there had been substantial reductions in the amount spent on agency nurses since a peak of £26.5m a decade ago, spending in the area has crept back up recently, and in the last financial year was the highest since 2008-09.
Labour health spokesman Neil Findlay said: "Only recently Audit Scotland highlighted the increasing use of agency and bank staff, as well as further reliance on the private sector, to plug the gaps in NHS staffing. However, yet again we see the Scottish Government advertising agency contracts when what we need is the right amount of trained staff in the right places at the right times to make our NHS fit for the 21st century."
As well as extensive use of nursing staff from external private agencies, the NHS is calling increasingly regularly on its own staff bank, which sees workers allocated to a department on a one-off, casual basis to cover shortages. In 2013-14, more than £118m was spent on staff bank nursing and midwifery workers, who unlike agency staff are employed directly by the NHS, up from £104m in 2012-13 and £90m in 2011-12.
A Scottish Government spokesman said the number of qualified nurses and midwives in the NHS in Scotland was at a record high, having risen four per cent under the current administration.
He added: "Spending on agency nurses and midwives has been cut by almost 50 per cent, from £18.4m in 2006-7 to £9.3m in 2013-14 and the use of agencies will fall further as recruitment for substantive posts continues. We are also working with boards to reduce their use of agency nurses and midwives by enhancing their own bank nurse and midwife staffing.
"The use of bank and agency staff helps NHS boards to respond to periods of planned and unplanned absence. Their use helps ensure service continuity."