Nicola Sturgeon has said she wants the power to nationalise Scotland’s railways after attacking ScotRail’s chaotic current performance as "unacceptable".

The First Minister went beyond current SNP policy, which is for a public sector franchise bid, saying Holyrood should have the chance to switch to all-out state control.

At present, the Scottish Government is responsible for letting the ScotRail franchise, with the current holder Abellio due to remain in charge until 2025.

However the rail infrastructure comes under the UK-wide public body Network Rail.

At First Minister’s Questions, Ms Sturgeon said both trains and track should be brought under Holyrood’s control through greater devolution to make nationalisation possible.

She said the SNP Government would “argue for full devolution of all powers over the railways, so that we are responsible for Network Rail as well as ScotRail and so that this Parliament has the opportunity to nationalise our railways”.

She said it would “undo the damage of privatisation caused by the Tories”.

It came as TSSA, the transport staff union, called on the SNP Government to stop bailing out ScotRail and issue a Remedial Plan Notice after passengers endured an estimated average of 80 cancelled trains per day in the first week-and-a-half of the new winter timetable.

The notice would require ScotRail to develop an urgent improvement plan to be agreed by Transport Scotland.

If this is unsuccessful, an “event of default” could arise, potentially leading to termination of the entire contract.

TSSA leader Manuel Cortes said: “[Transport Secretary Michael] Matheson should be more like Scrooge going forward and demanding that either Abellio meet their targets or hand back the ScotRail keys. Time for him to get tough.”

Ms Sturgeon's reference to nationalisation, meanwhile, went further than stated SNP policy.

In its 2016 Holyrood manifesto, the SNP said the party would merely ensure a public sector body was able to bid for a future rail contract, when the franchise lapsed.

While in last year’s general election manifesto, the SNP said its MPs would argue for the devolution of Network Rail to get “a more effective and efficient rail service”.

Nor is there a reference to rail nationalisation in the 2013 White Paper on Independence.

That said that once the current ScotRail and Caledonian Sleeper franchises ran out, the government of an independent Scotland would, “under existing European legislation, have the opportunity to consider all options for the delivery of passenger services, including public sector options”, but it did not identify nationalisation as one of those options.

That was despite stating the Royal Mail would be renationalised after independence.

SNP MSPs also voted against a Labour motion backing nationalisation just last month.

Scotland’s railways were last fully in public hands more than 20 years ago.

State-owned British Rail ran them from 1948 to 1993.

A gradual Tory privatisation then began in 1994 that transferred them to the private sector by 1997.

Mr Sturgeon’s comment came after she was pressed by the Scottish Tories about the current misery on Scotland’s railways as a result of hundreds of ScotRail cancellations.

Acting Tory leader Jackson Carlaw said punctuality was at its worst for 12 years, there were staff shortages due to training for a winter timetable, and delayed rolling stock.

Asked if train passengers were owed an apology, Ms Sturgeon said: “Yes, I do. ScotRail has made it clear that it regrets the cancellations and delays that have been caused. Let me be perfectly clear: the level of cancellations - this week, in particular - has been unacceptable.”

She said ScotRail caused 144 cancellations on Monday and around 40 on Thursday.

Mr Carlaw said new official figures showed around 5000 cancellations or partial cancellations a year “caused entirely by ScotRail”, despite ministers telling ScotRail to improve.

Ms Sturgeon said: “Progress is being made but it is not good enough.”

Mr Carlaw said Ms Sturgeon needed to ensure a train network “fit for purpose” in 2019.

Ms Sturgeon’s spokesman was later unable to say what rail nationalisation might cost.

He said: “Our position is to pursue a public sector bid. We don’t have those [nationalisation] powers. It’s not within our gift to do away with the franchise process.”

Former UK Labour rail minister Tom Harris, who recently authored a report warning about nationalistion, said: “If the First Minister believes that rail nationalisation is the answer, she’s asking the wrong question. Most delays to passengers are caused by publicly-owned Network Rail. Ownership is not the silver bullet that our politicians think it is.

“Instead of stating a publicly owned railway would be automatically superior, they should explain what practical measures it would take that the current operator is not. Relying on re-nationalisation as a magic cure-all risks disappointing voters and passengers.”

Labour MSP Colin Smyth said: “If Nicola Sturgeon was serious about nationalisation she wouldn’t have instructed her MSPs go vote with the Tories against Labour’s plans to bring ScotRail back into public ownership.”

Scottish Tory transport spokesman Jamie Greene added: "Going back to the days of the curled up sandwiches and British Rail is not the solution for Scotland’s railways."

ScotRail said re-nationalisation was not a matter for it.

ScotRail managing director Alex Hynes said: “We’re sorry to customers for the disruption to services in recent weeks. We know the impact this has on your day, and are working flat out to get things back to normal.”

A Scottish Government spokeswoman said: “Unique in the UK, the Scottish Government secured powers to accept bids for future rail franchises in Scotland from public sector organisations through the Scotland Act 2016. This was after repeatedly being denied that right by successive Labour and Conservative governments.

“The Scottish Government must let rail franchises in accordance with the UK Railways Act 1993, which requires open competition as rail franchising and competition policy remain reserved to the UK Government. Network Rail is a UK public body and, although its activities in Scotland are specified and funded by the Scottish Government, it is ultimately accountable to the UK Government.

“For the recently announced UK rail review to be meaningful, it must consider devolving all rail matters to the Scottish Ministers.  Until this happens, we cannot consider the full range of options for running the railways in Scotland for the benefit of our passengers and communities.”