The Advertising Standards authority has received "around 70 complaints" about the ad for the instant-win games brand GameStore, which appeared online as part of a campaign last month.
In the campaign Camelot, the owner of the National Lottery, contrasts situations where people have no chance of success with GameStore’s one-in-four odds.
The "missing" ad, created by Abbott Mead Vickers BBDO, shows a woman walking down a busy road and putting up a poster on a lamp post about her missing cat.
Copy then reads "no chance", implying that the woman has no chance of finding her cat. It then cuts to the same woman playing GameStore on her smartphone and the copy then says "1 in 4 chance".
A spokesman for the ASA said the general nature of the complaints is that the ad is offensive or distressing because it insinuates the cat has been run over and killed.
He added: "We are assessing the complaints. No decision on whether there are grounds to investigate has been made."
A spokeswoman for Camelot said: "The ad in question is one of a series of six different ads for our GameStore range of instant win games. Shown only on certain online channels and video-on-demand services, we wanted the campaign, which finishes this month, to come across as tongue-in-cheek and not to be taken too seriously.
"The ad is entirely fictionalised and no cats actually appeared in it. Nonetheless, we are aware that a small number of people are unhappy about the ad and we’re really sorry if we’ve unintentionally caused any offence or distress. We will certainly pass their feedback to the relevant teams here."