"She wasn't on duty, she was on her way to start duty."
He said the arrest was all the more worrying because people often relied on taxis to get them home safely after they had been drinking.
"It's tantamount to a betrayal of the trust placed on cabbies by members of the public to provide a safe, reliable and sober service," he said.
"Apart from the fact that it was during the daytime, it's also the fact that it's someone of that calibre, which most people wouldn't expect.
"And it wasn't just a little bit over the limit - I mean, taxi drivers shouldn't have any alcohol anyway."
New Zealand Taxi Federation chief executive Tim Reddish said taxi companies generally had a zero alcohol policy and the New Zealand Transport Agency would "almost certainly" suspend the woman's passenger endorsement licence.
"Pending the outcome of the court case if she is convicted they will revoke it and she will be very lucky if she ever got it back again."
He said instances like this were "very, very rare" and whatever capacity the woman was travelling in, it was a "really dumb" thing to do.
"If she was just in her private capacity and driving her taxi but not working, then she's really dumb because she will lose her taxi licence."
The Transport Agency could not be contacted for comment.
Mr Scoble said staff manning the Traffic Alcohol Group checkpoint said a number of drivers had complained how pointless it was setting up alcohol checkpoints during daylight hours but yesterday's result showed there was a genuine risk.
"This latest arrest follows a number last year where drivers were found intoxicated behind the wheel during the day.
"A number of drivers said the officers should be out catching burglars instead of picking on motorists but as a mater of fact about the same time the woman was being processed a man was also arrested in relation to thefts ex-car.
"Irregular, frequent checkpoints on our roads not only act as a deterrent to drink drivers, they are also very effective in disrupting criminal activity. Not everyone who drives is a criminal but most criminals drive and we know from experience that impromptu vehicle stops are a very effective deterrent."
The woman's arrest comes after a series of Transport Agency advertisements that show passengers' reactions after they are told the driver of the car they are in is high on drugs.
