Analysis, produced by used car database Cardata, shows that during one of the busiest months of the year, 33% of calls were left unanswered. A further 13% rang long enough for an answering machine message to click in.
Alarmingly, more than 4,000 people paid for and advertised the wrong telephone number altogether.
"If a dealer advertising the car you were keen on didn’t bother answering the phone, you would immediately think he didn’t care about doing business with you," says Andrew Sobell, marketing manager of Cardata."
In terms of regions, the North East recorded the lowest connection rate with more than 56% of calls not being answered, compared to the border area of Cumbria and Southern Scotland where just over 2 in 5 calls went unanswered.