[6] The Act applied only to protected animals from halfway through their gestation or incubation periods (for mammals, birds and reptiles) or from when they became capable of independent feeding (for fish, amphibians, and the common octopuses).

The project must also pass an ethical review panel which aims to decide if the potential benefits outweigh any suffering for the animals involved.

Having undergone a defined sequence of training, a researcher can apply for a PIL permitting specified techniques to be carried out on named species of animals.

[8] The 'project' level of regulation is governed by the granting of a "project licence" (PPL) to a suitably qualified senior researcher.

The report concluded that "virtually all witnesses agreed that the UK has the tightest system of regulation in the world" and that it is "the only country to require an explicit cost/benefit assessment of every application to conduct animal research.

In 2005, Patricia Hewitt, then British Secretary of State for Trade and Industry, called the Act "[among] the strongest laws in the world to protect animals which are being used for medical research.

"[10] A 2006 report by Animal Aid called the Act a "vivisectors' charter", alleging that it allows researchers to do as they please and makes them practically immune from prosecution.