Only a quarter of trains arrive in Wick on time, official new figures have revealed.
Calls for urgent action have been made after the new data was released by rail operator ScotRail.
Trains travelling north on the Far North Line are amongst the poorest performing in Scotland, with 74.3% of trains into Wick arriving late and 56.4% arriving in Tain behind schedule.
ScotRail admitted the last few months across their network had been “challenging” – but said that the overall performance figure for the country sits at 90.8% – higher than in England and Wales.
But Scottish Labour Highlands and Islands MSP Rhoda Grant criticised the service.
Mrs Grant, who is also vice-president of campaign group Friends of the Far North Line, said: “Most passengers accept that there are times when disruption can’t be avoided but people shouldn’t have to put up with services that arrive late more often than they arrive on time,” she said.
“The fact that only 25.7% of trains into Wick and 43.6% of trains into Tain are arriving on time is unacceptable. The SNP transport minister needs to get a grip of what is happening on our railways and explain exactly what will be done to tackle delays and improve reliability.”
Trains arriving in Inverness were on time 56.3% of the time, Dingwall 58.8% and Invergordon 65.1%.
Stations in the west were better performing with 66.2% on time to Oban, 89.2% to Fort William and Mallaig 80.2%, although Kyle was only 51.4%.
A spokeswoman for ScotRail said that overall figures put them ahead of the equivalent for England and Wales and in 10th out of the 23 train operating companies in the UK.
She added: “We have had a challenging few months due to the ongoing industrial action, the big infrastructure works at Queen Street and the programme to electrify the line between Glasgow and Edinburgh.
“This has undoubtedly contributed to the fact that we are slightly behind our demanding target for performance.
“We have agreed an action plan with Transport Scotland about how we pull this back up to the level we would expect.”
