NHS 24 bosses have apologised for the "serious incompetence" that resulted in a £41.6 million overspend on a new IT and call-handling system.

The estimated cost of the project has spiralled from £75.8 million to £117.4 million with years of delays.

MSPs on Holyrood's Public Audit Committee have been told the final amount could reach £125 million after a decision in November to withdraw the system from service shortly after it first launched due to concerns about patient safety.

Conservative MSP Mary Scanlon accused NHS 24 management of having "really seriously let people down". "It is pretty serious incompetence," she said.

John Turner, NHS 24 chief executive between September 2008 and July last year, told the committee: "I'm very sorry for the fact the implementation of the Future Programme is delayed so much, meaning that patients and staff are not yet receiving all the additional benefits and that there's been a considerable over-run on the public purse.

"This is a matter of disappointment, frustration and deep regret. I absolutely accept my responsibilities as accountable officer at the time and offer my full apology."

He told MSPs he felt "very let down" by the legal team at Pinsent Masons who had worked on the project and by former NHS 24 director of finance and technology Robert Stewart, who he said had not advised him of omissions from the contract with technology supplier Capgemini.

Mr Turner told the committee he had been "astounded" to discover crucial sections relating to the performance of the system had not been printed out when the final version of the contract was prepared.

Asked why a final check of the 1,000-page document was not carried out before he signed it in March 2012, he said: "That is a question that has tormented me since this came to light."

He also said there had been a "fundamental flaw" in the technology provided by Capgemini.

MSPs also heard from interim chief executive Ian Crichton, who apologised "unreservedly" for the situation.

He said: "From the very start, the organisation vastly underestimated the scale and complexity involved in bringing such an ambitious programme into service and it has struggled to cope.

"Our challenges have been systemic, in the sense that none of the governance around the programme has successfully mitigated the risk enough to deliver on time and budget.

"Although many mistakes have been made and I can understand the extreme concern and dissatisfaction of the committee, I think it's important you understand that NHS 24 has learned from that."

Mr Crichton said he remained concerned about the checks and balances in place for large-scale IT projects.

"Fundamentally, in my view, the governance framework around IT is deficient."

Speaking after the evidence session, committee convener Paul Martin said: "The issues around the management of NHS 24's ICT contract are deeply troubling with significant consequences for the public purse.

"While the management and oversight of this contract raised particular concerns, there are fundamental problems with capability and central government's management of ICT contracts.

"For that reason, the committee is inviting the Scottish Government's relevant accountable officers to appear before it to answer questions around the governance and oversight of such projects."