The payments were made by track owner Network Rail after members of the Rail, Maritime and Transport union (RMT) staged a series of 19 days of stoppages between June and January.
The pay and conditions dispute did not involve Scottish Government-owned ScotRail staff but the train operator was only able to run a fraction of its normal services because signallers employed by Network Rail were among those who took part in the walkouts.
The dispute was settled last week after union members voted to accept a revised pay offer worth between 9.2 and 14.4 per cent depending on salary levels. That averted threatened further strikes on Thursday and Saturday.
In a response to a Freedom of Information request by The Scotsman, UK Government-owned Network Rail said on Monday that it had paid ScotRail Trains £6,510,466 to date “in compensation in relation to industrial action”.
The money has been paid under an established process to compensate for lost revenue and costs, although an industry insider said there was a debate about whether that fully covered long-term revenue loss, such as from those put off train travel.
ScotRail said its compensation claim was “ongoing” after it was able to run only 9 per cent of its normal 2,150 services, limited to the Central Belt, during the first six strikes in June, July and August, when 1,956 a day were cancelled.
That increased to 18 per cent during the remaining 13 strikes between October and January, with 1,763 trains a day halted.
However, knock-on disruption on the day following each stoppage meant ScotRail could only operate 86 per cent of trains then, with 301 trains a day unable to run.
Derek Marchant, its finance director, said: “The dispute between the RMT trade union and Network Rail had a major impact on ScotRail, both financially and on our ability to operate services, despite no members of ScotRail staff being involved.
“On the days of strike action by RMT members of Network Rail, ScotRail could operate only a small proportion of the normal timetable, with the days surrounding strike action also resulting in service cancellations. Compensation for this is available through the well-established industry processes for such situations. ScotRail’s claim for compensation is ongoing.”
RMT Scottish organiser Mick Hogg said: “Under the indemnified policy ScotRail has with the Scottish Government, this is what ScotRail is entitled to claim.
“It makes no sense a public-sector employer paying another public-sector employer compensation, all funded by the taxpayer. You could not make this nonsense up even if you tried.”
Scottish Conservatives transport spokesperson Graham Simpson said: “This demonstrates the high cost to the public purse of industrial action on our railways.
"Unions need to consider the damage they are doing when they take such action. We all need to work together to deliver improvements to rail across the UK.”
RMT members at ScotRail staged two days of strikes in October in a separate pay dispute.