Japan is poised to resume commercial whaling this week after leaving the International Whaling Commission.
When it originally took the decision last December, the country said it was no longer possible to whale commercially under IWC rules.
Japan says it will only conduct the practice in its territorial waters and exclusive economic zones.
However, there is opposition to the move. In London, around 50 people took part in a protest organised by Britain-based animal protection groups.
The rally marched towards the Japanese embassy carrying placards and calling for tougher whale protection.
The IWC imposed a commercial moratorium in the 1980s due to a dwindling whale population.
Japan switched to what it called research whaling but now says stocks have recovered enough to resume commercial hunting.
However, critics of the programme say it was simply a cover and the meat ended up being sold to restaurants anyway.
Those who market whale meat claim it's a healthy food, high in protein and low in calories.