Consumers have been warned that they need to own a valid TV licence to watch live television broadcasts on their mobile phones.
Anyone watching TV events on their mobile phone or computer, who does not already have a TV licence, could face a £1,000 fine.
TV Licensing said it had previously prosecuted people successfully for watching live TV on their PCs.
The majority of people already have a TV licence and they would not require a separate licence for PC or mobile phone, it said.
"However, if a customer currently has no licence, they will need to obtain one to watch live programmes on their PC or mobile.
"Any device used to watch or record TV programmes as they are being broadcast, such as through an aerial, or otherwise distributed, via broadband, internet streaming or wi-fi, must be covered by a valid licence.
"This is the case whether you are watching or receiving a programme via a PCTV, mobile phone, PDA (personal organiser) or any other device.
"Any licence evader caught risks a criminal conviction and a fine of up to £1,000, plus court costs - and they still have to pay for a TV licence."
Broadcasts made for mobile phone networks or exclusive transmissions of live events would usually be exempt.