A "perfect storm" is brewing for the nursing workforce following a "boom and bust" approach to staffing, the profession has warned.

The Royal College of Nursing (RCN) Scotland has called on ministers to take action, arguing that modest increases in nursing and midwifery staff are not keeping up with demand.

The number of nurses, midwives and health visitors in Scotland rose by 1% between 2009 and 2015, according to a new report from the RCN, up from 42,670 to 43,085.

Vacancy rates for nursing posts rose from 3.7% to 4.2% in June 2016, the RCN said.

Meanwhile, student nurse intake numbers fell by a quarter between 2005/06 and 2012/13, dropping from 3593 to 2713. Numbers began to rise again in 2013/14.

The report also highlights pressures arising from the age profile of nursing staff.

In 2006, just over 40% were aged 45 or over, but in 2015 this had risen to well over half.

RCN Scotland director Theresa Fyffe said: "The last few years have been characterised by a boom and bust approach to nursing workforce planning, with many of our health boards cutting the number of nursing staff, simply to balance their books - and then having to try and recruit more nursing staff as demand for services soared.

"This is no way to run our health services. Scotland's population is getting older and more and more people are living with more complex conditions. Demand for health care is going through the roof.

"And you only have to look at the latest NHS vacancy rate - which went up from 3.7% to 4.2% in June 2016 - to know that the very modest increase in staff is just not keeping pace with demand, with a number of health boards really struggling to recruit enough nursing staff."

Health secretary Shona Robison pointed out the nursing workforce had increased by 2100 since 2006, a rise of 5.2%.

She said: "Rises in nursing and midwifery vacancies are due to the creation of new posts in health boards, mainly as a result of information from our innovative workload and workforce planning tools which help health boards to plan for the number of staff they require.

"We are committed to training and retaining our nursing staff and we will increase the number of trainee nurses and midwives by 5.6% for 2016/17 - a fourth successive rise."

Robison added that the government "is committed to retaining the nursing and midwifery bursary and free tuition fees in Scotland".

Opposition parties called the report another "stark warning" on the NHS.

Scottish Labour health spokesman Anas Sarwar said: "The SNP government has ignored previous warnings from staff and that can't be allowed to happen again.

"The SNP previously cut number of training places for nurses and midwives by more than a fifth and over 2000 nursing jobs were cut.

"The RCN warned then those choices were short-sighted and would lead to problems and that is exactly what has happened.

"With the rising numbers of nursing and midwifery vacancies, at more than 2500, we are now seeing a direct impact on patient standards and increased pressure on over-worked and under-valued staff.

"We already know that 9 out of 10 nurses think their workload has worsened, and over three quarters of them say that finances have become worse."

Scottish Conservative shadow health secretary Donald Cameron said the government must "explain why it hasn't created more student places when it knew the workforce was ageing, and why hiring patterns have been so erratic".

"The NHS in Scotland has never been busier, but it's being run by an SNP government which constantly lets it down," he added.

Scottish Liberal Democrat health spokesman Alex Cole-Hamilton said: "This is the latest stark warning from NHS staff who are struggling under enormous pressure.

"The shortages we are seeing are only going to get worse if the Scottish Government does not get serious about supporting the health service."