The mother of an autistic boy has accused rail staff of mocking her son at Paddington station.

Sarah Hilary said she was left humiliated when two employees of Great Western Railway allegedly jeered at her and her 17-year-old son after she asked whether they could take an earlier train than the one they had booked on Sunday evening.

She said staff accused her of “trying it on” and she was made to feel like a criminal. GWR has apologised, saying an investigation had been launched.

Hilary, a crime writer who lives in Bath, made a formal complaint. She said she and her son arrived two hours early for their train and asked staff at the help desk whether they could be transferred to an earlier one because her son was “so overwhelmed” by the station environment.

“I tried to explain how difficult it was for my son but they spoke to us both rudely, accused me of trying it on and humiliated us in front of other passengers,” she said.

In a tweet, Hilary continued: “When I tried, again, to explain my son was autistic, one of the men said: ‘Yeah, so’s mine,’ in a voice that made it clear he was really saying ‘pull the other one’. I have never been spoken to so cruelly and horribly in any public place, least of all by customer service staff.”

She added: “It takes a lot of courage for my kid to travel by public transport, and he still feels the stigma of his diagnosis, so to be humiliated and jeered at – and accused of lying and fraud – was a huge setback and so unnecessary.”

A GWR spokesman said: “We are sorry to learn of Sarah’s experience … All of our staff are given autism awareness training with a leading autism charity as part of our customer service training programme. We are investigating the issues raised and are grateful to Sarah for bringing this to our attention.”

Hilary said she was grateful for the apology and she understood that staff at senior level were appalled by what had happened.

Hilary said she was surprised by the response she had received to her tweets and the number of people who said they had similar experiences.

“This is not just about GWR but using transport generally. The number of incidents where people are spoken to rudely, where parents or foster parents with an autistic child get someone saying ‘he does not look disabled’ thrown out there.”

Hilary said she was concerned that it was hard for autistic people to fight their own corner in this regard and that was why she had spoken out.

In July a comedian criticised Great Western Railway after she was left feeling “harassed and humiliated” for using a disabled space for her mobility scooter.

Tanyalee Davis, who has a form of dwarfism, said a guard on a GWR train threatened to call the police if she did not leave the space to make way for a woman with a pram.

A GWR spokesman said the company was “collectively horrified” by what had happened.