The cost of a new NHS 24 IT system has soared by 73% to £130m, auditors say.

The project, which failed and was shut down a few weeks after launch last year, costs about £500,000 every month it stays offline.

The failure could threaten the financial future of NHS 24, which provides health advice by telephone and online, Audit Scotland reported on Wednesday.

Between 2012 and 2015, NHS 24 was loaned £20.8m by the Scottish Government to help it meet costs associated with the delays launching the system.

It has repaid just £400,000 so far and the total cost of the project will not be available until has launched successfully, auditors said.

Meanwhile, Audit Scotland has raised separate concerns about the financial position of NHS Tayside in a report also published on Wednesday.

Auditors warned there is a "significant risk" the health board will not meet its "unprecedented" savings target of £58.4m for the financial year 2016/17.

NHS Tayside has received £24.3m in financial support from the Scottish Government over the last four years to help it break even.

The health board received £5m to cover costs including staffing and prescribing in 2015/16 alone and Audit Scotland said there is a strong chance it will need further support in future.

Auditor general for Scotland Caroline Gardner said: "Each of these health boards is experiencing prolonged and considerable challenges which continue to have an impact on the way they operate and deliver services.

"While action is under way to try to address these issues, there's no quick fix available and recovery will take time.

"It's important that the Scottish Parliament and the Scottish Government closely monitor progress to ensure circumstances do not worsen, to the detriment of staff and service users."

Audit Scotland will publish a report on the overall financial health and performance of NHS Scotland later this month.

NHS 24 chief executive Angiolina Foster said: "We fully acknowledge the findings in the Auditor General's report. Delays in this major IT programme have led to a significant increase in costs and a review of how the organisation operates to fully understand why we were unable to implement the new system.

"Following a detailed review of the 2015 attempt to go live, we are planning a phased approach to the delivery.

"We are pleased to report that last week, we successfully went live on the first phase of the revised programme with six planned care services now up and running on the new telephony system.

"The next stage is partnering with one health board to ensure all aspects of implementation are secure, prior to a broader national roll out during 2017."

Lesley McLay, chief executive of NHS Tayside, said: "NHS Tayside, like many other public sector organisations, is facing a number of challenges over the coming years.

"Today's report from the auditor general sets out some of the challenges which we experienced in 2015/16 and I would like to assure communities in Tayside that we have already taken decisive actions to address these to ensure NHS Tayside returns to sustainable financial balance in the coming years.

"The auditor general acknowledges that this recovery will take time. Over the past 18 months we have been building a Five-Year Transformation Programme for Tayside to drive forward redesign and change.

"This is led by our clinical staff and the programme is now well under way. However, it is important that we are realistic about the timescales involved in this transformation."