Dame Anita Roddick has refuted claims The Body Shop is "getting into bed with the enemy" after backing a decision to sell the cosmetics chain to L'Oreal.
Animal rights groups including Naturewatch and Uncaged have pledged to boycott the Littlehampton-based firm following the £652 million deal.
L'Oreal has not tested its cosmetics on animals since 1990 - but it continues to use new ingredients tested on animals.
Dame Anita and husband Gordon Roddick are to bank £117.4 million after backing the board's decision to sell The Body Shop to the French firm.
Dame Anita said the deal with L'Oreal was not a "sell-out" but a chance to strike a fairer deal for the world's poor.
She said: "The most exciting thing about this is that L'Oreal is asking us to teach it about community trade, which is the best poverty eradicator in the world."
But Naturewatch has urged its supporters to boycott The Body Shop.
Director John Ruane said: "Now that The Body Shop is owned by L'Oreal, Naturewatch is unable to endorse The Body Shop as cruelty free. While its own policies may reflect a cruelty-free policy, that of its new parent company L'Oreal fall drastically short.
"We encourage all consumers to use their purchase power to send a very clear message to The Body Shop and L'Oreal that they will not use cosmetic products or ingredients that have been tested on animals."
Ethical Consumer magazine is also urging consumers to boycott the chain.
Spokeswoman Ruth Rosselson said: "It's ironic a company well known for its anti-animal testing stance should sell out to one that tests on animals and which has yet to show its commitment to any ethical issues at all."
Alison Plaumer, head of Brighton and Hove Green Party's animal rights working group, said she was "appalled" by the deal.
She said: "We want to eradicate cruelty in our society, not promote it. I am appalled they are being taken over by L'Oreal.
"The Body Shop does fantastic work on fair trade and sustainability but now its parent company is one which still uses ingredients tested on animals and that's terrible."
The deal marks the end of an era for Dame Anita and her husband.
The couple, who live near Slindon, West Sussex, opened their first shop in Kensington Gardens, Brighton, in 1976 and still own an 18 per cent stake in the company.
The takeover will be another windfall for Iain McGlinn, the former Sussex garage owner who lent Dame Anita £4,000 to set up the first store 30 years ago.
He is the group's single biggest shareholder and stands to make £137 million from his 21 per cent stake.
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