The justice secretary has rejected calls from opposition MSPs to resign after it emerged one of his officials was accused of interfering with an independent police watchdog report.

Michael Matheson faced criticism at Holyrood on Tuesday over the affair after a string of emails about the matter were released to the Sunday Post after a freedom of information request.

The emails given to the newspaper showed Kate Frame, the Police Investigations and Review Commissioner (Pirc), accused Donald McGillivray, deputy director of the Scottish Government's police division, of "governmental interference" after he asked for the publication of a highly critical report to be delayed.

The Scottish Government were already facing accusations of interference in nominally independent bodies after it emerged Matheson asked the Scottish Police Authority to reverse its decision to allow the chief constable to return from special leave amid allegations of gross misconduct.

Conservative justice spokesman Liam Kerr asked the minister "when will he do the honourable thing and resign?"

Kerr said: "We now know there is a deeply embedded culture of secrecy and central interference and that tone is set from the top.

"Michael Matheson should have the good grace to realise what that means and if he doesn't we should spell it out.

"He has fallen short of the standards expected in high office. He does not have the moral credibility to do his job."

The minister replied: "I'll continue to do the honourable thing and that is to do my job properly."

He added later: "The decision on what action was appropriate in light of those issues was clearly a matter for the Pirc to make and the Pirc as an independent body has made it clear that there has been no interference in this publication.

"As the Pirc has also stated they decided it was appropriate to proceed as planned in the publication of the report and I fully support the independent decision making of the Pirc in this matter."

Matheson said he had only become aware of his official's email last Thursday when Pirc had advised the administration the emails were to be released to the Sunday Post through freedom of information laws.