Michael Matheson is on his “last life” and will be sacked if any more mistakes are unearthed by the investigation into his £11,000 iPad bill, the Herald understands.

Senior sources said the Health Secretary had only kept his job because the First Minister, the father of two girls, understood his instinct to protect his family during the scandal.

However Mr Yousaf also believed that Mr Matheson should have handled the issue far better from the beginning and his patience was almost exhausted.

"He thinks Michael did it for the right reason, but he's down to his last life," a source said.

The FM grimly defended Mr Matheson at FMQs on Thursday over what he called an “honest mistake”, but conspicuously failed to say the Health Secretary had always told the truth. 

The Herald understands that if Mr Matheson changes his story again, or more embarrassing facts emerge, his place in the cabinet will be deemed untenable. 

The cross-party group that oversees the running of the Scottish Parliament last week agreed to look at whether Mr Matheson properly billed taxpayers for expenses related to the iPad.

Mr Matheson’s teenage sons ran up huge data roaming charges watching football by using his Holyrood iPad as a hotspot on a family holiday in Morocco over the New Year.

After providers EE billed the parliament for £11,000, officials raised the matter with Mr Matheson and he queried the sum and handed in his iPad to be checked.

It emerged he was using an old SIM card that he had been told to get replaced, but he remained unaware of how so much data had been used.

On November 16, he told MSPs: “I had not used the iPad for any purpose other than parliamentary and constituency business and could not understand how the costs could be so high. In the absence of a clear explanation of how such a large bill could have happened, I thought it appropriate to make a contribution, through office allowances, of £3000 towards the cost.”

It was this £3000 claim on his parliamentary expenses that was published as part of Holyrood’s regular expenses update earlier this month, triggering the row.

Despite Mr Matheson lacking a “clear explanation” for the bill at the time, his expense claim required him to assert the money was needed to cover a legitimate parliamentary expense - an assertion he was not in a position to make.

The claim is now likely to be the focus of the Scottish Parliamentary Corporate Body investigation, which could also involve a referral to Holyrood’s standards committee.

Despite learning on November 9 that the bill was down to his sons, Mr Matheson maintained in a media interview four days later that no one else had used his iPad and continued to blame the out-of-date SIM card, even though this by itself was not responsible.

That led to opposition parties doubling down on their calls for Mr Matheson to quit or be sacked, claiming the case was emblematic of the Government’s kneejerk secrecy. 

At FMQs, Mr Yousaf let his frustration show through, but stood by Mr Matheson.

He said his health secretary had made “mistakes in the handling of this entire episode”, adding: “As a father of two children, including a teenager, I can understand the motivation to protect one’s family, but I agree with others in the chamber that it should not have been handled in this way.”

One SNP MP said they had been stunned by Mr Matheson’s actions, saying all financial matters in their office were triple-checked and assessed for public perception.

However an SNP MSP was more sympathetic and said Holyrood’s IT department had questions to answer for allowing the out-dated SIM card to remain in use.

The person said it was the department’s responsibility not merely to flag the problem but to fix it by replacing it with a new one, adding: “They did that for me and others.”

Tory MSP Craig Hoy: “Time has all but run out for Michael Matheson to straighten his story and salvage what little is left of his discredited reputation as Health Secretary.

“He’s now used up eight lives and is drowning in half-baked cover-ups.

“Every passing day of this scandal creates more questions than answers - and the biggest question remains why Humza Yousaf has yet to sack him in light of his blatant refusal to do the right thing and resign.”