Misleading adverts from group-buying websites that offer deals and discounts have prompted a rising number of complaints.
The Advertising Standards Authority (ASA) has had almost 100 complaints in the last year, with KGB Deals generating a quarter of them.
And 23 off the 24 complaints about KGB Deals were upheld. That means the deals were misleading and the adverts had to be changed.
The sites have exploded in the last couple of years, all promising great deals which they send to millions of people in daily emails.
But critics have pointed out that many of the so-called deals – particularly those offered at hotels – are often more expensive than those firms give direct to customers.
Also, some offers have such short deadlines it can prove impossible to take them up in time.
Others are oversold so that restaurants, for instance, have been unable to cope with the demand, meaning some people's vouchers expire before they can use them.
On a more prosaic note, many sites clog customers' in boxes with inappropriate or useless offers. Expensive, teeth-whitening deals seem to be offered every other day, for instance.
The country's most well-known group-buying site – Groupon – had nine of 10 complaints upheld, according to Which?
The US-owned site was criticised by the Office of Fair Trading (OFT) earlier this year for sending out misleading offers. The ASA also upheld two rulings against Wowcher and three against Living Social.
Meanwhile, the OFT is examining the offerings of 35 other sites.