A drink-driver caught by police was eight times over the limit, a senior officer has said.
The 36-year-old woman was stopped by Cleveland Police in Redcar and tests showed she had 275mg of alcohol per 100ml of breath. The legal limit is 35.
Details of the incident last September were revealed by a Freedom of Information request and published by the Middlesbrough-based Evening Gazette newspaper.
Ed Turner, temporary Chief Inspector of Cleveland and Durham Specialist Operations Unit, said: "I am shocked and astounded by the high level of that reading.
"However that is quite a unique and isolated example.
"I am delighted we managed to capture and prosecute that person."
The reading was taken at 7.25pm. The circumstances of why the woman was stopped were not clear.
Mr Turner said most people recognise the dangers of drink-driving on a night out, but many did not think about the next morning.
Mr Turner said: "You really need to be careful and allow the time for the drink to get out of your system before driving."