Caledonian Sleeper today announced a further delay to the introduction of its brand new trains on Highland routes.
The £150 million fleet with double beds and ensuite toilets and showers will not start operating to Fort William, Inverness and Aberdeen northbound until 7 July.
London-bound services using the new trains will start on 8 July.
The date is more than a month later than previously announced and a year after the trains were originally due to have begun running the overnight services to London.
Transport secretary Michael Matheson described the setback as "extremely disappointing".
He also said it was "unfortunate" that some passengers would have booked on the Sleeper because of the new trains.
Operator Serco blamed the need to minimise the risk of "teething problems" after glitches marred the launch of the trains on the Edinburgh and Glasgow routes last month.
It also pointed to the complexity of the "Highlander" service, which involves sections of the train dividing and being joined together in Edinburgh, involving new couplers, which have been reported to have caused problems.
The trains' debut on the Edinburgh and Glasgow routes was brought forward unexpectedly from the end of May to 28 April.
The other routes were due to switch to the new trains on 2 June.
Caledonian Sleeper managing director Ryan Flaherty said: “As we now look forward to the arrival of the iconic Highland Caledonian Sleeper trains, we are determined to ensure each and every carriage is ready for our guests when we bring them into service.
“The new service has been years in the making and its introduction into service has been a hugely complex undertaking with many challenges.
"Additionally, the Highland route is significantly more complicated than the Lowland route, and this is a key factor in our decision to phase in the introduction of the new trains.
"It will give us the ability to closely monitor how the trains are performing and ensure we can provide a consistently high-quality service for guests.
“We appreciate guests on the Highland route won’t be travelling on new trains as expected in June, but we believe this decision ensures guests will receive the quality service they expect from the new trains.
"By the second week in July our new trains will be operating across all routes.”
Mr Matheson said "further production issues" had caused the delay.
He said: "Manufacturer Caf has not supplied sufficient vehicles, in a service-ready state, to allow Caledonian Sleeper to commence its Highlander service as planned."
He said the delay "will also allow Caf to rectify faults identified in initial service of [the new ] Mark 5 vehicles.
The minister said problems had been encountered when the first trains ran on 28 April.
"Full passenger operation revealed a number of on-board issues, including with water supply to berths.
"While further delay is extremely disappointing for all involved, it is important to ensure trains are introduced in exemplary condition, and with a focus on quality of provision that will benefit the service in the long term.
"It is unfortunate that some passengers have already booked travel on the basis that new trains would be introduced on 2 June. "
However, Mr Matheson said he was pleased at the "largely positive reaction" to the new trains.
He said: "The scale of change in passenger provision is impressive."
Passengers booked to travel from the planned 2 June start date will be refunded any difference in cost if they paid for enhanced facilities like ensuite rooms, or offered a refund if they no longer wish to travel.
Scottish Liberal Democrats transport spokesman Mike Rumbles said: “The lack of preparation for this service is astonishing.
"The sleeper train is a vital link for people from the north of Scotland to the rest of the UK.
"The contract is already a year overdue, now passengers are being told they will have to wait another month for the service to begin.
“What makes matters worse is that many people have already reserved their tickets and some of them may have booked the trip just to experience the new trains.
"I cannot believe the Scottish Government and Serco have come to this realisation only 13 days before launch."