Worldwide, the industry now generates about $2.1bn per year, it says.

The group commissioning the report, the International Fund for Animal Welfare (Ifaw), says whaling countries would gain from a switch to whale watching.

However, Iceland's delegate here said the two industries were compatible and could grow together.

Iceland recently announced a major expansion of its fin whale hunt and plans to take 150 of the animals this year, along with up to 100 minke whales.

"Whale watching is clearly more environmentally sustainable and economically beneficial than hunting, and whales are worth far more alive than dead," he told BBC News.