A driver caught on the phone at the wheel stuck his middle finger up - only to quickly realise he had just insulted a team of undercover police officers.
The mortified motorist had realised he was being filmed but was unaware it was by officers on patrol, police said.
The footage was captured by officers who were out conducting mobile phone enforcement in an unmarked vehicle.
The offender can be seen with his phone to his ear as the police drove up alongside him.
Once the driver realised he was being filmed, he allegedly put the phone down and stuck his middle finger up.
Police say his response showed the 'total disregard' some people have for the law.
Avon and Somerset Police Roads Policing teams said on Twitter: "Officers conducting mobile phone enforcement in an unmarked vehicle observed this driver on his phone.
"His reaction, before noticing that the person recording him was a Police Officer, shows the total disregard some people have for the law & road safety!"
It comes just months after one foul-mouthed driver got a telling off and was reported after swearing at officers for pulling him over.
Leicestershire Police officers had been taking part in Operation Tramlines, where they use an unmarked lorry to patrol motorways in the region to catch out drivers breaking the law.
The Roads Policing Unit had been posting their findings to Twitter all week, with one driver in particular getting a shout out after a four-letter verbal volley at police officers when they pulled alongside a motorist who cut them off to get to a junction on the motorway.
Officers said at the time: "#OpTramline again today. If you cut up the unmarked HGV in order to dive off at a junction we’ll want to speak to you. When we pull alongside you to speak to you, it’s a poor decision to tell us to **** off not realising who we are!"
