The Independent Television Commission has received more than 200 complaints since Levi's started screening a jeans advert starring Kevin the hamster on Thursday.
The response from viewers was unprecedented, said the ITC, and represented a very quick reaction to the ad.
Most complaints are that the advert is in bad taste and that it is upsetting for children. The advert shows a seemingly happy and healthy Kevin running on his wheel until his wheel breaks.
Depression sets in and the advert ends with a dead hamster being prodded with a pencil.
The advert had a restriction placed on it to stop it being shown during children's programmes, but it could still be shown before the 9pm watershed.
"I'm not sure that a 7.30 restriction would have made much difference with the aged 10 to 11 hamster-owning age group," said an ITC spokeswoman.
The advert has now been pulled, but a spokesman for the company said that it had only been scheduled to run for one weekend.
Levi's provoked outrage when it ran an advert starring a transsexual in a taxi - its advertising has always been considered cutting-edge.
The Levi Strauss spokesman added: "The aim of the campaign is certainly not to shock or offend but to entertain the viewer.
"No animals were harmed or suffered any discomfort during the filming of the ad."
Tony Readwin, the National Animal Welfare Trust's spokesman, branded the advert "disgusting" and said that the company had plainly intended it to be as provocative as possible.
He added: "It was obviously going to cause concern for a lot of people and it's got a lot of coverage."
Mr Readwin likened the advert to the much-criticised Benetton clothes campaign.
The RSPCA was less critical, saying the advert of the "dead" hamster was a matter of taste for viewers.
It had not been informed of any animal cruelty, it added.
The advert is yet to be investigated by the ITC, but complaints about offence are not frequently upheld; misleading adverts tend to take up more of the ITC's time.