Dumbarton MSP Jackie Baillie has called for ScotRail/Abellio to be stripped of the rail franchise.
Ms Baillie says recent figures show that the train operator is falling behind on its own passenger satisfaction targets.
She added that the official autumn 2018 survey, published in January this year, reveals that the firm scored 79 per cent in overall passenger satisfaction, trailing behind the franchise agreed target of 88.5 per cent for 2018/19.
ScotRail/Abellio has specific key performance indicators linked with passenger satisfaction, and Ms Baillie says it is clear they are failing to meet their own targets.
The survey, she says, also revealed that only 39 per cent of passengers are satisfied with how the franchise handles delays.
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Ms Baillie said: “It is a regular occurrence that Helensburgh, Balloch and Dumbarton passengers endure delays alongside being crammed in like sardines thanks to a lack of carriages during rush hour services.
“Passengers have had enough, and this is reflected in this year’s satisfaction levels being well below ScotRail’s own targets.
“The Labour party noted that the SNP government had secretly fiddled with ScotRail passenger satisfaction targets.
“Had the original satisfaction targets stood, the SNP would have been able to strip the franchise from Abellio.
“For the sake of passengers and taxpayers, ScotRail continuing in this current state is unacceptable.”
Read more: Jackie Baillie MSP slams government over ScotRail franchise
A ScotRail spokesperson said: “We have submitted a remedial plan to Transport Scotland, and will work with colleagues there to reach a remedial agreement.
A Transport Scotland spokeswoman said: “Any calls to rip up the current contract early are short-sighted.”
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