Jeremy Colman was first appointed to the auditor general role in 2005
The former Auditor General of Wales has been arrested on suspicion of possessing indecent images.
Jeremy Colman, 61, resigned with immediate effect on Wednesday as head of Wales' public spending watchdog, the Wales Audit Office.
South Wales Police said it was called in the following day to investigate, following allegations of pornography on a workplace laptop.
Mr Colman, from Dinas Powys, has been bailed until 3 March pending inquiries.
He had resigned from the £170,000 post without giving a reason.
The Wales Audit Office said later in a statement he had gone after a review into "matters of personal conduct".