A small group of experts in philosophy, conservation and dolphin behaviour were canvassing support for a "Declaration of Rights for Cetaceans".

They believe dolphins - and their whale cousins - are sufficiently intelligent and self-aware to justify the same ethical considerations given to humans.

Recognising cetaceans' rights would mean an end to whaling and the captivity of dolphins and whales, or their use in entertainment.

The move is based on years of research that has shown dolphins and whales to have large, complex brains and a human-like level of self-awareness.

This has led the experts to conclude that although non-human, dolphins and whales are "people" in a philosophical sense, which has far-reaching implications.

Ethics expert Professor Tom White, from Loyola Marymount University, Los Angeles, author of In Defense of Dolphins: The New Moral Frontier, said: "Dolphins are non-human persons. A person needs to be an individual. If individuals count, then the deliberate killing of individuals of this sort is ethically the equivalent of deliberately killing a human being."

The US authors brought their message to the annual meeting of the American Association for the Advancement of Science (AAAS) in Vancouver, Canada, the world's biggest science conference.

Psychologist Dr Lori Marino, from Emory University in Atlanta, told how scientific advances had changed the view of the cetacean brain.

She said: "We went from seeing the dolphin/whale brain as being a giant amorphous blob that doesn't carry a lot of intelligence and complexity to not only being an enormous brain but an enormous brain with an enormous amount of complexity, and a complexity that rivals our own. It's different in the way it's put together but in terms of the level of complexity it's very similar to the human brain."