Mathew Notley, of Longstone, also allegedly upset a colleague by showing him a pornographic picture on his mobile phone.

The 29-year-old – who manned the trains' catering trolley – faces the threat of being sacked after being accused of gross misconduct by First ScotRail.

The complaints against him centre on allegations about his behaviour on trains on the Edinburgh-Inverness line.

He is said to have pressed two girls to give him their phone numbers and web addresses despite being warned they were only 15.

One passenger also described how he went on to do the same thing to girls who looked about 13 years old.

First ScotRail is understood to have received two complaints from passengers about Mr Notley. A First ScotRail conductor has also complained that the steward, unprompted, showed him a picture of a young naked woman on his mobile phone.

The incident involving the schoolgirls is said to have taken place on July 14. A further complaint alleges he acted in an inappropriate way to two girls on the same Inverness to Edinburgh service the following day.

Leaked First ScotRail documents say the train conductor intervened in this case and was so concerned that he got the passengers' parents to meet them off the train when it reached Perth.

Mr Notley, who is living in a bed and breakfast in Longstone, declined to comment when approached by the News.

Police today said they had not been made aware of complaints about Mr Notley's behaviour.

It is understood that Mr Notley has been with First ScotRail for around 18 months and was subject to Disclosure Scotland checks when he started, which came back clear.

A First ScotRail spokesman said: "A member of staff has been suspended following a complaint. A full investigation has been carried out and a disciplinary hearing will be held in the near future."

Mr Notley is originally from the south-east of England.

It is thought he previously worked as a bus driver and delivery driver before joining First ScotRail last year.