A major new health service IT system is expected to go £23 million over budget after a series of problems and delays, Scotland's public spending watchdog has found.

Auditor General for Scotland Caroline Gardner has raised concerns about the NHS 24 project as well as the accounts of NHS Highland and NHS Orkney in a series of reports to the Scottish Parliament.

The reports detail "poor financial management" in NHS Highland and "weaknesses" in NHS Orkney during the financial year 2013/14.

Both boards faced pressures due to the costs of hiring locum doctors to cover medical posts, it was found.

The cost of technology to improve NHS 24's telephone and online services for patients has soared from an expected £29.6 million to £38 million, Ms Gardner revealed.

The project, part of NHS 24's Future Programme, was due to be completed last year but is now expected to be finished in 2015 with a final price tag of at least £52.6 million.

Delays have been caused by a dispute between NHS 24 and the supplier of the technology over its performance and patient safety concerns, the report says.

NHS 24 has received additional cash, known as brokerage, of £20.76 million from the Scottish Government to help fund the programme, which it plans to start paying back next year.

The report warns there are "high risks" to NHS 24 achieving its five-year financial plan from 2014/15, which includes targets to break-even or have a surplus each year.

It says: "The auditors have highlighted a number of significant risks to the board in achieving the planned savings and managing the planned repayment of the brokerage between 2014 and 2017.

"The auditors concluded that achieving future financial targets will be extremely demanding."

Weaknesses in financial management at NHS Highland were a major factor in the board requiring an extra £2.5 million from the Scottish Government to break even late in the financial year.

The health board overspent on the operating costs for Raigmore Hospital in Inverness, a separate report said.

It added: "Other factors contributing to the need for brokerage were financial pressures in the acute sector from costs associated with hiring agency staff, particularly locum doctors, and meeting national waiting times targets."

Spending on hiring agency staff grew from £5.3 million in 2012/13 to £9.6 million in 2013/14, an increase of 83%, the report says.

The health board's financial position is expected to remain "challenging" for the next five years.

NHS Orkney needed £1 million brokerage from the Scottish Government to break even, a final report details.

It said: "The board recruited a number of staff to key posts in 2013/14, but it has underlying recruitment problems and has not been able to fill some posts despite several recruitment campaigns.

"This means it needs to use locum doctors and agency nurses to maintain levels of patient care. Agency locum doctors in particular command much higher rates of pay than staff employed directly by the board."

It is the fourth time that NHS Orkney has needed additional funding to break even in the past five years.

The board has received a total of £5.38 million, and has repaid £1.32 million, according to the report.

A spokeswoman for the Scottish Government said the reports were taken "very seriously" and the Government is working with the health boards to address concerns.

She said: "Protecting front-line health services is an absolute priority of this Government, and that's why we have not only protected the NHS budget but increased it.

"However we must always strive to be as efficient as possible with taxpayers' money, and we welcome that health boards have met their financial targets for the last six years and exceeded their efficiency targets, allowing more than £1.5 billion to be ploughed back into front-line services over the same period."

NHS 24 chief executive John Turner said: "NHS 24 is developing a programme to update our technology systems for the future. We are disappointed the system has not been implemented yet, but we will only deploy it when it is safe to do so. We continue to develop the system with our suppliers meantime.

"NHS 24 is working very closely with the Scottish Government in relation to the financial management of this programme.

"We would like to reassure the public that our current systems are working extremely well across Scotland, with the 111 service supporting more people than ever before and demonstrating public confidence in our unscheduled care service. People should not hesitate to contact NHS 24 if they need to make use of our services."

Cathie Cowan, NHS Orkney chief executive, said: "NHS Orkney met all its financial targets for 2013/14 by breaking even on both its revenue and capital budgets, whilst also receiving an unqualified audit opinion on the accounts.

"The board does however accept the recommendations in the AGS report and continues to work both internally and with the Government in response to the issues raised on financial management."

Garry Coutts, chair of NHS Highland, said the report was taken "extremely seriously" and actions were being taken to tackle any failings.

He said: "We note that it is reported that we advised the auditor that the full extent of overspending and weaknesses in financial control at Raigmore Hospital did not emerge until late 2013/14, following the appointment of a new management team in December 2013.

"We are confident that the hospital's new management team is working assiduously to address budget management issues there.

"NHS Highland is currently being supported by the Scottish Government through the Being Here programme, with £1.5 million invested in testing innovative ways of recruiting to healthcare professionals, and particularly GPs, in rural areas of Scotland. We hope that, in time, this will help us to reduce on expensive reliance on using locums.

"The report is right to point out that we recognise the significant challenges we face in identifying and delivering savings.

"But I wish to assure the people we serve that we will do so without compromising on the quality of the services we provide and on patient care. We are determined to continue to do better and to continue to improve our services within the resources made available to us."

Liberal Democrat health spokesman Jim Hume MSP said: "On NHS 24, taxpayers face the prospect of paying millions of pounds more than was promised for improvement works that are now years behind schedule. The Health Secretary needs to come to Parliament and explain how the Government let this crucial project get so far off track.

"The SNP's record on the health service is one of underinvestment, missed treatment targets, bed shortages and now delays and massive overspends on NHS 24. They have let down patients, NHS staff and taxpayers alike.

"While ministers were busy talking up independence, their mismanagement of our NHS was running down crucial services across Scotland."