Commuters are being warned that if they are caught watching porn on public transport they will be reported to the police.

Transport for London (TfL) has issued the alert following a number of reports of people watching x-rated material on their tablets or smart phones while travelling on the Tube or buses.

Siwan Hayward, TfL’s Head of Transport Policing, said: “We do not tolerate any unwanted sexual behaviour on our transport network.

“We work closely with police taking all reports extremely seriously.

“If someone has made you feel uncomfortable, for example by viewing pornographic material, please tell the police or a member of our staff.”

Last month TfL launched an investigation following claims a Tube worker was seen watching porn on his tablet at Wembley Park station.

According to a shocked commuter the man was watching the x-rated film on his tablet as he supervised busy platform.

He told the Sun newspaper: “I was at Wembley Park station when I saw the platform supervisor sitting in his cab intently viewing a tablet.

“On closer inspection I noticed it was porn, and he continued to watch it even when a train came into the platform.”

He added: “I could clearly see it was a Japanese film involving a man and a woman. I asked him a question, he held the device to his chest and then continued to watch it as I walked away.

“He didn’t look shocked at all – he acted like it was a completely normal thing.”

Anyone who suspects a commuter is watching porn is urged to tell a staff member.