MINISTERS are facing calls to clamp down on the use of expensive agency nurses to plug staffing gaps in the NHS, after it emerged they were being relied on four times more often than when the SNP won its historic majority.

Scottish Labour went on the attack over the NHS, pointing to a damning Audit Scotland report which revealed a litany of problems in the health service, highlighting staffing and financial pressures, missed targets and declining performance in the face of soaring demand for services.

Among the other issues raised by the watchdog was a rising reliance on agency nursing and midwifery staff, which cost three times as much as more commonly used NHS 'bank' staff who agree to carry out extra shifts. Spending on the external workers rose by 68 per cent in real terms in 2014/15 compared to the previous year, leaving a bill of £16 million.

Agencies charge the NHS almost £43 per hour on average, with costs as high as £85 in remote areas, compared to £15.62 for NHS staff volunteering to work above their contracted hours. Audit Scotland warned that relying too much on temporary staff may pose risks to patient safety.

Labour said that in 2011, the year the nationalists won a majority at Holyrood, spending on the agency workers was just £3.9m, claiming the surge in private sector spending was evidence of inadequate planning.

The claim drew a strong response from Shona Robison, with a spokesman for the Health Secretary accusing opponents of launching a "boomerang attack," pointing out that the current figures were far lower than when Labour was in power. In 2005/06, under the Labour and Liberal Democrat coalition, the NHS spent almost £27m on agency nursing staff.

The bitter row comes with health set to become a dominant issue in the run-up to next year's Holyrood elections, and days after Nicola Sturgeon said she would campaign on the SNP's record in power.

Labour insisted the increase in spending on agency nurses represented a "sticking plaster" approach to the health service. Jackie Baillie, the party's public services spokeswoman, said: "The SNP have said they want to be judged on their record – that record is quadrupling spending on private nursing staff in our NHS. For our NHS to face the challenges of the next decade and beyond every penny of the health budget needs to be spent wisely.

"The SNP have cut the health budget, and have overseen a huge increase in private spending on nursing staff since forming a majority government. Audit Scotland has revealed the sheer scale of the problems within our NHS under the SNP. This increase in private spending suggests poor workforce planning going back years."

In the Audit Scotland report, published yesterday, the watchdog said that total spending on the NHS had been cut by 0.7 per cent in real terms over the last six years.

Ms Robison has said resource spending, which is used to fund day-to-day costs such as staffing and excludes capital expenditure, had grown by almost six per cent in the 60 months up to 2015/16.

Her spokesman said: "This is yet another boomerang attack from the Labour party, who seem to have forgotten their own record on agency nurses. Spending on agency nursing and midwifery staff last year was lower than when Labour left office and indeed, Labour spent more on agency staff in just their last three years than the SNP has in the eight years in which we have been in power.

"Despite rising demand and an NHS treating record levels of patients, in 2014/15 agency staff made up just 0.3 per cent of the total nursing and midwifery workforce. This is down to careful workforce planning, and a significant increase in the number of staff working in Scotland’s NHS - including an additional 600 nurses and midwives over the last year alone."