Michael Matheson, Scotland’s embattled health secretary, has apologised “unreservedly” after admitting he failed to properly disclose that his sons had largely run up an £11,000 iPad bill which he had initially charged in full to taxpayers. In a personal statement to MSPs on Thursday, Matheson said he had referred himself for possible investigation by parliament for breaching its code of conduct, as he fought against mounting calls to resign from opposition leaders. During first minister’s questions on Thursday, Douglas Ross, the Scottish Conservative leader, called on Matheson to quit, and came as close as parliamentary rules allowed to accuse the health secretary of lying to MSPs. Ross said Matheson, an SNP politician, had misled Holyrood: “It wasn’t just a mistake, it was dishonest.” Matheson admitted his teenage sons had watched football, using his parliamentary iPad as a data hotspot, while they were on a family holiday in Morocco. According to figures released by Holyrood officials, nearly 3.8Gb of data was used on 2 January, at a cost of £8,666. Close to tears at several points, Matheson said: “Disclosing this information about my family has been extremely difficult. Mistakes have been made by me and by my family.” Matheson said one of his sons had helped him set up a hotspot on the iPad in Morocco and told MSPs that parliamentary officials had agreed he could use the iPad as such. A Holyrood spokesperson said it had no record of that being raised or agreed. The scandal erupted last week after it emerged that he had racked up a £10,935 data bill on his parliamentary iPad during a week-long Christmas holiday in Morocco, and refused to explain why. He initially told Holyrood’s authorities those charges were all legitimately incurred on parliamentary business; Holyrood officials accepted his assurances and agreed to pay nearly £8,000 of that bill directly. Officials also allowed Matheson to put the remainder of the costs on to parliamentary expenses, leaving taxpayers to foot the entire bill. The parliament has since announced a wholescale review of all iPad and data billing rules. It also emerged Matheson had ignored instructions from parliamentary officials to update his SIM card, which was by then out of contract, had not updated his iPad data settings, and had failed to tell officials he was taking the device overseas. After two days of questioning last week about how such a large bill could be incurred on parliamentary business on holiday, Matheson, who has a combined parliamentary and government salary of £118,511, agreed, on 10 November, to personally reimburse Holyrood in full. Matheson told MSPs he had learned from his wife the previous evening – the day the row first blew up – that his sons had used parliamentary data to watch football. He said he failed to disclose that immediately because he wanted to protect his family from public scrutiny. The health secretary said he eventually told Humza Yousaf, the first minister and Scottish National party leader, on 14 November that his sons had used his data, and told Yousaf he planned to make a personal statement. Matheson had also been challenged by reporters on 13 November as to whether there had been personal use of the iPad; he had denied it. Opposition parties say the controversy raises substantial questions about Yousaf’s leadership. They believe he should have sacked Matheson for misleading himself and parliament. Yousaf “is the last person in Scotland still believing his minister’s ridiculous claim”, Ross said. Jackie Baillie, Scottish Labour’s deputy leader, said the saga raised “serious questions” about their judgment, in part because Matheson’s attention had been diverted from tackling NHS Scotland’s numerous crises. It also raised questions over whether he had kept his iPad and its confidential information secure.