A TEEN who sprayed a fire extinguisher at a train and its driver has been warned he's on track for jail — after 'not bothering his backside' with a community payback order.

Lee Millar has had additional punishments added to his original sentence and was told by a sheriff that his next destination will be a '6ft x 12ft cell' if he continues to flout the court ruling.

Millar, 19, repeatedly shouted before grabbing the firefighting equipment and spraying its contents during a serious mob disturbance late at night at Drumfrochar Station in November 2016.

Prosecutor Meghan Glancey told Greenock Sheriff Court: "At 10pm there was a report of a disturbance on a train.

"The train arrived at the locus and the accused and a group of youths were seen to get off the train, with one of the group carrying a fire extinguisher.

"The accused took hold of the extinguisher and sprayed it on the train and through the driver's window.

"The contents of the extinguisher landed on the driver's clothes and on the control console within his cab."

Fiscal depute Miss Glancey added: "Police arrived a short time later and officers observed the fire extinguisher to be on the track."

Millar, of Dempster Street in Greenock, last year admitted to behaving in a threatening or abusive manner likely to cause a reasonable person to suffer fear or alarm.

He also pleaded guilty to repeatedly shouting, removing a fire extinguisher and spraying it at the train and driver.

But he has failed to comply with unpaid work and supervision directives handed down by the court.

Sheriff Derek Hamilton told him: "This order was imposed as an alternative to custody and you've basically not bothered with it.

"You've not bothered your backside for supervision, or anything."

Millar had also been accused of running amok with a gang of others onboard the train, banging its interior and acting aggressively towards a ticket examiner, but this was removed from the charge against him as part of a negotiated plea with the Crown.

The rail line to Wemyss Bay has been hit by a series of incidents of disorder and vandalism.

Defence lawyer Aidan Gallagher said: "Mr Millar appears to have previously associated with negative peers, and alcohol has also been an issue.

"This explains why he has been in non-compliance with the order.

"He's made positive changes in his life, now has his own tenancy and is accompanied in court by his mother and grandmother.

"Mr Millar is now described as having a pro-social lifestyle, and should he perhaps get another opportunity he would take that with both hands."

Sheriff Hamilton told Millar that he was going to impose a 'half-way measure' by extending his unpaid work to 150 hours and placing him on electronic tagging curfew for a month.

The sheriff said: "You will not get another chance with this, Mr Millar.

"If you get into further bother your restriction of liberty will not be to your house, it will be within 6ft x 12ft cell."