The footage is usually produced by animal right activists, some of whom aim to promote vegetarianism or veganism.

These films only represent a minority of the industry and they have brought a sharp reaction from farmers, who carry out high-welfare production.

Under pressure to protect their agricultural industries, many states in the US have looked to introduce laws, which would prevent undercover footage being taken on livestock farms and in some states to prevent people taking on jobs under false pretences.

This week, a broad spectrum of national interest groups have signed a statement opposing any proposed "ag-gag" legislation. They believe that this would lead to critical information about the production of milk and meat products being suppressed.

Their statement says: "Not only would these bills perpetuate animal abuse on industrial farms, they would also threaten workers' rights, consumer health and safety, and the freedom of journalists, employees and the public at large to share information about something as fundamental as our food supply. "

Laws have already being passed in Montana, North Dakota and Kansas, with similar proposals in Iowa, New York, Minnesota, Indiana, Illinois, Missouri, Nebraska and Utah.

Whilst undercover footage often exposes inexcusable cruelties, it also makes allegations about practices which are legal and acceptable in commercial practices.

Showing these practices to the consumer, without an explanation of why they are carried out is seen as damaging to the industry by many.

But instead of preventing undercover investigations from taking place altogether, should the industry be reaching out to consumers and explaining why certain practices take place? They are in the majority of cases to benefit the animal or the consumer.

On the other end of the scale, undercover footage in abattoirs in Indonesia made the Australian beef industry, consumers and politicians change current practices, which will lead to improved welfare of those animals exported live.