ScotRail has apologised to passengers for "unacceptable service" but warned disruption will persist as drivers continue to be trained.

In a statement to customers, the rail operator's chief admitted they had "fallen below the standard you expect and deserve."

The operator was ordered by the Scottish Government to submit a plan for how it will address falling performance levels in December following additional cancellations and disruption when a new timetable came into force.

ScotRail Alliance managing director Alex Hynes said: "We are very sorry to ScotRail customers for our unacceptable service in parts of the country recently.

"While our teams work hard every day to deliver the service you demand, the reality is that we've fallen below the standard you expect and deserve."

Mr Hynes explained how services had been cancelled so drivers and conductors could be trained on new trains and new routes.

He added: "We are working flat out to train conductors and drivers on Scotland's railway so that we can return services to normal. But that will still take several weeks.

"Since 9 December we have trained 60 drivers and conductors, which is good progress, although we know we need to do more.

"But training will still take several weeks, and that means disruption will be ongoing for the foreseeable future."

The training has also been hampered by late delivery of trains by suppliers, including Hitachi and Wabtec, Mr Hynes claimed.

A dispute by the RMT union about overtime and rest-day working was also blamed for increasing disruption.

ScotRail is urging customers to check the status of intended journeys before travelling.