RAIL operator First ScotRail is launching a crackdown on fare dodgers after finding that one of its most popular saver tickets could be subject to widespread abuse.

Random spot checks carried out last week found 150 people misusing Flexipass tickets, which allow infrequent commuters to save around a third of the cost over 10 journeys.

The crackdown was revealed after allegations of heavy handedness by staff at Bishopbriggs Station during a ticket check.

ScotRail said the security operation was vital to protect revenues and ensure that fare-paying passengers are not treated unfairly.

It warned that those caught abusing the system from today could be prosecuted rather than required to purchase a new ticket.

The Flexipass scam is thought to involve passengers boarding trains for short trips without filling out the date on their ticket, allowing them to use the ticket again if they disembark at a station with no automatic ticket barrier.

Last week's operation by ScotRail's Fraud and Security team focused on commuters in and around Glasgow, with 70 passengers caught and made to buy a single ticket at Bishopbriggs and 80 at Lenzie. But it's suspected the abuse takes place across Scotland, as Flexipasses are available on dozens of routes.

A ScotRail spokesman said: "We have feedback from honest customers that there is a risk of fraud and that they want the conditions of use to be enforced.

"From today extra staff will be deployed to tackle the misuse, supported by a campaign of posters and announcements advising people they must hold valid tickets for journeys.

"We have a duty to protect revenue and the campaign will continue until the issue is resolved."

James King, Scottish board member for rail watchdog Passenger Focus, welcomed the crackdown but said he would be concerned at any move towards withdrawing the ticketing option.