There needs to be a systemic review of out-of-hours hospital care in Wales, the public services ombudsman has said.
A snapshot of 12 cases investigated by the watchdog over five years shows "inadequate standards of care" given to patients, including at weekends.
Nick Bennett said although not typical, a pattern suggested they were not "one-off" incidents.
Mark Drakeford said only one example had happened while he was health minister but he took it seriously.
He told BBC Wales he wanted to share the report with senior doctors and understand whether some of the issues raised by cases dating back to 2010 had now been addressed or "whether there are still issues where we can do more or do better".
Mr Bennett found "significant clinical failings" in the cases and said poor quality out-of-hours care often related to inadequate consultant supervision.
"This report emphasises the need for more effective and equitable clinical care to be provided seven days a week with greater consultant supervision, as well as the requirement for health boards to ensure their staff are adhering to the guidelines that are already established and accepted as good practice," he said.
Themes arising from the cases include:
- Inadequate consultant cover across seven days
- Delays in medical review and lack of consultant review
- Lack of senior supervision for junior medical staff
- Failure to meet pre-existing standards of care and established guidelines.
Mr Bennett also found the variation in practice between hospitals and even between wards in a hospital "both interesting and worrying".
The report is set against a background of a