A Bulgarian truck driver stopped by North Wales Police was estimated to have worked 23 hours without a sufficient break.
The driver, who was stopped on the A55 at Llanfairfechan on 28 March, had also not paid the HGV Road User Levy whilst using a Bulgarian-registered HGV.
Police also discovered a false record from the previous day, which had disguised the fact he had not taken a daily rest.
PC Eifion Jones of the Roads Policing Unit said: ''On examination of the tachograph records, we found that the driver had not taken a break from driving.
"We estimate he had worked the previous 23 hours without taking a valid rest break. The maximum break estimated in this is the four hours spent on the ferry travelling from Europe to mainland UK."
The driver also failed to produce a digital tachograph card, while the truck had no rear number plate and was emitting excessive smoke from the exhaust.
The truck, which was carrying food products from Portsmouth to Ireland, was immobilised for 24 hours by the DVSA and the driver was issued with five traffic offence reports.
By Ayesha Khatoon