The Caledonian Sleeper rail service has been ordered to improve by the Scottish Government after its operators admitted the journey has been “unsatisfactory”.
The acknowledgment came after the service between London and Scotland was hit by strike action, technical faults and the late delivery of trains.
Serco Caledonian Sleepers Ltd said an improvement plan was now in place.
The service has been hit with a catalogue of problems since the new fleet launched in April.
These include passengers being locked out of cabins, corridor toilets locked out by computer error, poor cabin cleaning that led to the contractor being sacked and no hot drinks available to passengers in the morning.
Between mid September and 12 October, only 63 per cent of services between London and Edinburgh were on time.
For sleeper services between Fort William, Aberdeen and Inverness to London, the figure was 72 per cent over the same period, although overall 80 per cent of trains were on time.
At its launch in June the revamped sleeper was described as a “hotel on wheels”.
The £150 million fleet consists of 75 carriages with en-suite double rooms. But the service has been beset by a string of problems.
In June, a technical problem – believed to be the application of emergency brakes – saw passengers stuck at Stafford and forced to complete their journey by bus.
Damage caused to wheels in that incident led to several days of cancellations and delays.
Two weeks later, a rescue train was sent to collect passengers stranded in the Highlands after a service from Fort William broke down.
In August, a Caledonian Sleeper train overshot Edinburgh Waverley station, only coming to a halt after emergency brakes were applied.
At the end of September staff took part in a 48-hour walkout over stress and workloads leading to multiple cancellations.
The improvement plan will attempt to address delays caused by the coupling and decoupling of trains at Carstairs and Edinburgh Waverley.
Serco Caledonian Sleepers said improvements would also be made to the reliability of electric and diesel locomotives, depot and station operations and communication with infrastructure operator Network Rail.
In a letter to the quango Transport Scotland, Serco Caledonian Sleepers said it was “with regret” that it recognised “a number of issues have contributed to a decline in right time arrival performance of the service”.
Scottish Transport Secretary Michael Matheson said Caledonian Sleeper’s performance had fallen below the levels expected by passengers and ministers alike.
He added: “This has been caused by a number of internal and external factors, which are being addressed by Caledonian Sleeper and its industry partners CAF, GB Railfreight and Network Rail.”
Mr Matheson added that the SNP Government continued to call for full powers over rail to be devolved to Scotland.