Stripping ScotRail of its contract to run the railways is on the table if performance fails to improve, First Minister Nicola Sturgeon has said.

Her warning to the under-fire rail operator came as Liberal Democrat MSP Mike Rumbles branded the published ScotRail improvement plan a "flimsy document" with "more pictures in it than detail".

Transport Scotland asked ScotRail to draw up the improvement plan in September following concern over performance figures and a summary was published last month, but Mr Rumbles said the full document should be made public.

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He also questioned when the service would improve, after ScotRail was fined £483,000 for failing to meet required standards for trains and stations.

Speaking at First Minister's Questions, he said: "Ministers are hiding behind commercial confidentiality and that's simply not good enough. The Transport Minister needs to publish the full plan with any really commercially sensitive information redacted. First Minister, we need some openness and transparency here."

Ms Sturgeon said: "There's no hiding behind any commercial confidentiality. The performance requirements for ScotRail are contained in the franchise.

"They're not meeting at this stage the requirement to have 91 out of 100 trains arriving at destinations within the industry-recognised punctuality measures.

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"They are sitting at around 89 trains per 100, that is why the Transport Minister has insisted on an improvement plan and why we continue to monitor their performance against that plan on a weekly basis.

"We will continue to do that because the travelling public deserve to know that their trains will run effectively, efficiently and on time, and we are determined to work through the contract to make sure that is the case.

"Of course, ultimately, if ScotRail do not meet their performance requirements, we have the option of terminating the option early, and that's very much an option we keep on the table."

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Dutch firm Abellio was awarded the franchise in 2015 for 10 years but ministers can strip the company of the contract after five years if punctuality falls below 84.3%.

More than 19,000 people have signed a petition calling on Transport Minister Humza Yousaf to ''make ScotRail bosses improve Scotland's trains or strip them of their contract''.

Abellio ScotRail managing director Phil Verster has previous said it would ''absolutely not'' reach the point where the number of trains running late could force the Scottish Government to end Abellio's contract.