The deal is tied to more flexible working to minimise disruption when new services are introduced next month.

It is also seen as an attempt to stem the exodus of drivers to better-paying operators such as Transpennine Express.

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ScotRail will be desperate for stability after passengers suffered months of disruption, much of it caused by staffing problems.

These have centred on the need to train drivers and conductors on four different types of new trains - twice as many as expected because of delays to the delivery of the two planned new fleets.

ScotRail has pledged to recruit 55 more drivers as part of a remedial agreement with ministers in March to improve performance.

On Tuesday, several MSPs called again for ScotRail operator Abellio to be stripped of the franchise.

Scotland on Sunday revealed in February that ScotRail was trying to persuade retired staff to return to the cab because it was so short.

According to figures from Aslef, the main drivers’ union, ScotRail is 39th in a pay table of 45 operators.

The deal will see drivers’ pay increase from £48,360 to £49,000 when extra services are added as part of a new timetable on 19 May.

It will be further raised to £50,000 in October and £51,500 in October next year.

The increases are conditional on more flexibility, such as holidays.

Drivers’ managers will also be permitted to cover shifts “as an absolute last resort to otherwise avoid a train cancellation and associated disruption for customers”.

Newly-qualified drivers who leave ScotRail within three years of the start of their training will have to repay all or part of their training costs, of up to £15,000.

Kevin Lindsay, Scotland district organiser for Aslef, has recommended approval.

He said: “This agreement, if accepted by my executive committee, will give ScotRail train drivers a more competitive salary and should allow Abellio to safeguard ScotRail services throughout the summer.”

ScotRail operations director David Simpson said: “It has been a challenging few months for Scotland’s railway, but we have been working hard with Aslef to address these challenges.

“We have agreed a package of productivity and flexibility improvements, which will help to deliver the service our customers expect and deserve, and secures important benefits for drivers.

“This is a good deal for ScotRail, our drivers, and our customers. We look forward to Aslef’s executive committee approving the deal.”

Train driving has proved to be hugely attractive, with ScotRail being swamped with more than 22,000 applications for 100 jobs during a previous recruitment drive in 2015.

However, Aslef said the firm had failed to ensure it had sufficient numbers.

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Scotrail drivers secure 6.5 per cent salary bump to £51,500