ScotRail has been ordered to come up with a remedial plan after failing to meeting passenger satisfaction targets.
The order came after the Scottish government said it would be "extremely difficult" for ScotRail to reach its 88.5% satisfaction target this year.
ScotRail is already dealing with another improvement order following a surge in train cancellations.
But the train operator has seen a slight improvement in overall performance in recent months.
ScotRail has faced a string of performance issues over the past year, including cancelling thousands of services because of staff shortages.
Transport Secretary Michael Matheson said the firm's latest score of 79% in the twice-yearly National Rail Passenger Survey (NRPS) meant it would be extremely difficult for ScotRail to reach its overall 88.5% average target for 2018/19.
He said: "These latest NRPS results are unsurprising and clearly linked to the recent poor performance. Too often passengers have been left disappointed and this must change swiftly.
"Having already issued one remedial plan notice, it is frustrating that another follows. ScotRail recognises the reasons for this notice and the direct link between train service reliability and customer satisfaction.
"I require quick action to ensure the ongoing record investment in infrastructure, fleets and staff quite rightly translates to better satisfaction levels and a more attractive service.
"Passengers want and deserve a railway which delivers the benefits of more seats and services on a consistently reliable basis."
ScotRail now has twelve weeks to submit a plan to improve its customer satisfaction rates.
And it has until 18 February to submit a separate plan to reduce the number of cancellations.
The Scottish government demanded this plan after the central belt of Scotland was hit by a series of cancellations 11 November and 8 December last year.
'Working flat out'
The problems came ahead of the introduction of a new timetable on 9 December, which promised 100 new services and faster trains.
But a week later ScotRail boss Alex Hynes apologised for further disruption and pledged to make improvements.
ScotRail's head of customer operations Phil Campbell said: "We run more than 2,400 services every single weekday, which is more than ever before, and our punctuality has recently reached its highest level since September last year.
"But we know there is much more to do, given the challenges we have faced in recent months.
"Everyone at Scotland's railway is working flat out to deliver the service our customers expect and deserve.
"We will submit a remedial plan to Transport Scotland within the timescale outlined."