An email sent by payment giant PayPal which promised customers a reward of £10 for using their account did not make it clear enough that not everyone would receive it, the Advertising Standards Authority (ASA) has ruled.
It upheld a complaint from a recipient of the email, an offer limited to the first 28,527 people to respond.
PayPal said that it had made this clear in the terms and conditions.
But the ASA said the ad must not appear in its current form again.
"We considered that consumers were likely to understand from the subject line and headline claim that they would receive credit worth £10 from PayPal, and the subsequent qualification was insufficient to counter that impression, so we concluded that the ad was misleading and breached the code," wrote the ASA in its ruling.