PinkStinks consists of three volunteers and zero funding. "Everything we do has to be cheap and cheerful, but noisy," says Abi Moore, co-founder of the campaign. It's a formula that seems to work, judging by the success the group has enjoyed since it was set up in 2008.
Moore and her twin sister Emma, head of information and publishing at voluntary sector umbrella body the NCVO, established the group to challenge the stereotyping of young girls.
Abi, a filmmaker by profession, had just returned from the US, where she had been making a documentary about a female scientist who was developing new cancer treatments.
"Paris Hilton was leaving prison and there was blanket news coverage of that pointless, tedious story," she says. "I started thinking about why we celebrate wealth, beauty and thinness rather than women treating cancer. What's happened to our culture and what is it doing to girls and boys?"
The sisters agreed to set up a website challenging the idea that girls should wear pink and be ultra-feminine.
Last year, it urged shoppers to boycott the Early Learning Centre for its "blatant gender stereotyping" of products. The story went global. "Teachers asked us for support packs and we had requests for our website to be published in Spanish," says Abi. The company refused to meet the group, but it was recognised for publicising the issue with a Sheila McKechnie Foundation campaigning award.
This year, PinkStinks wrote to supermarket giant Sainsbury's about its "sexist" labelling on children's clothes. Princess and nurse outfits were labelled 'girls', and soldier, pilot, superhero and even doctor outfits were labelled 'boys'.
Abi says the supermarket was initially dismissive, but relentless pressure from the group and its 11,000 Facebook friends paid off when Gwyn Burr, customer director at Sainsbury's, wrote to the group.
"It isn't acceptable to suggest certain professions are the reserve of any gender," she wrote. "This is an error and one I am seeking to address. The new labels, which will be non-gender-specific, will go on the next allocation of clothing, so will be in store from July."
Abi admits she was astounded. "We didn't think they'd listen to us," she says.
PinkStinks' over-arching aim is to initiate a culture change. "It's ambitious and we're not sure we can do it," says Abi. Pink, she says, is symbolic of an issue that goes beyond the colour of clothes.
"What we are challenging is the way big companies are defining girls," she says. Without funding, that won't be easy. The organisation hopes the strength of its message, its bold approach and its use of social media will help it to continue to enjoy the kind of success many bigger organisations can only dream of.
Abi used to work for Amnesty International, which doesn't accept donations from government, and she thinks charities that do take private and public funding can get neutered.
"A lot of big charities are very cautious," she says. "They have fear. It's easier to make bold statements when you have nothing."