THE operator of the Caledonian Sleeper has blamed "issues beyond our control" for a technical glitch which has wreaked havoc with its booking system for the past month.

Passengers were unable to make online bookings for seats or berths on the flagship Scotland-London service for around two weeks from January 10 after IT problems crashed the site.

And nearly a month on, Serco have been unable to iron out an ongoing glitch which is currently preventing travellers from making any reservations on the southbound Highlander service from mid-May until early-December.

One passenger dubbed the fiasco a "complete boorach".

He added: "I had to cancel things down in London, it was pathetic. If something goes wrong, you come up with something else – but just to sit there and say 'we can't do anything until out IT system is mended' makes you lose all confidence in their ability to run it."

Serco took over the running of the Sleeper for a 15-year term in April 2015, when it was hived off from the main ScotRail franchise, and is in the running for the new CalMac ferries contract.

A previous IT fault one week after Serco took over left some foreign visitors turning up to discover they were booked on non-existent coaches.

The Sleeper was also embroiled in controversy in December when members of the RMT union staged a 24-hour walkout immediately before Christmas in protest at train defects which they claimed Serco had failed to fix, including disconnected smoke alarms, inoperable toilets and faulty heating and lighting systems.

Serco insisted the issues had either been fixed or were in the process of being resolved.

Meanwhile, the service has also faced disruption since the beginning of January by repairs to the Lamington Viaduct, which has seen the Sleeper temporarily axed at Edinburgh Waverley.

Instead, the Lowlander terminates at Glasgow while the Highlander, running on the East Coast Main Line out of London King's Cross, bypasses the Scottish capital and heads straight for Aberdeen, Inverness and Fort William to reduce journey time.

David Simpson, production and safety director at Caledonian Sleeper, apologised for the booking glitch and urged affected passengers to make telephone reservations on 0330 060 0500.

He added: “We have been having a number of technical problems with the booking website, due to issues beyond our control.

"I’m pleased to say that we’ve managed to fix almost all of these apart from one that is still affecting guests booking seats on the southbound service from Fort William from mid-May to early December and another that means the website is showing weekday trains arriving and departing from Euston instead of King’s Cross.

"At present our Highlander service for Fort William, Inverness and Aberdeen is using Kings Cross station to provide the best service for guests while our normal route is blocked because of the damaged viaduct."