In a joint open letter, the heads of train operator ScotRail and infrastructure firm Network Rail admit services connecting Glasgow to Ayrshire, Renfrew-shire and Inverclyde have been below par and promise problems with reliability and trains running on time have now been addressed.
It blamed poor performance on engineering works made as part of a recently completed £170million upgrade of the route between Glasgow and Paisley, together with vandalism and "severe weather".
Punctuality has been con- sistently below target over the last year, with more than one-quarter of all services suffering delays at times.
Steve Montgomery, managing director of ScotRail, and David Simpson, Network Rail's route managing director for Scotland, said: "Punctuality and reliability levels have now returned to target, but we remain committed to bringing about further improvement.
"Our priority has been to return our services back to the levels you deserve, and we have worked closely to achieve this, with much better performance in recent months."
Despite the problems, both ScotRail and Network Rail have insisted the infrastructure works carried out as part of the Paisley Corridor Improvement (PCI) programme and introduction of 38 Class 380 electric trains last year would lead to an improvements in services along the route.
The PCI works had originally been part of the Glasgow Airport Rail Link, but continued after the latter project was axed.
Two extra platforms have been built at Glasgow's Central Station and other improvements include construction of a third track east of Paisley and full re-signalling of the route.
The project has led to railway closures at weekends and overnight, as well as problems affecting daytime services on the route.
The upgrade is expected to lead to new services being introduced from December this year, though the Scottish Government is yet to announce how it will use the additional track capacity.
More than nine in 10 train services along the route are now officially classed as being on time, with more than 95% of trains between Glasgow and Wemyss Bay on time – according to industry figures which show a significant improvement on last year.
The admission was welcomed by business groups yesterday, with the Chambers of Commerce in Ayrshire, Renfrewshire and Greenock saying improvements to train reliability would enhance the areas' reputations.
There was support too from East Ayrshire Council and South Ayrshire Council, whose chief executive, David Anderson, said: "Here in South Ayrshire we pride ourselves on our fantastic location and the great transport links available, so I'm pleased rail punctuality and reliability levels are now much closer to those our residents, workers and visitors expect and deserve."