The hashtag was started by a blogger named Debz, in response to the Loose Women panelist's controversial views about people "below or above a certain weight".
"I don't believe stores should stock clothes below or above a certain weight," Jamelia said on Tuesday 21 April.
"They should be made to feel uncomfortable when they go in and can't find a size."
Debz tells HuffPost UK Lifestyle the issue has now become "bigger than Jamelia".
"The hashtag going viral was amazing," Debz says. "I was speechless. It made me feel proud that women of all shapes and sizes were feeling empowered enough to speak out.
"So many people have shared their stories online which made me realise the conversation is now bigger than Jamelia.
"This isn't an issue just about plus size women. It's petite women and 'acceptable' size women and even men who are affected and it was heartwarming to see so many people coming together."
HuffPost UK blogger and plus-size model Georgia Grogan has got involved with the campaign, sharing the photo below:
— She Might Be Loved (@GeorginaGrogan_) April 22, 2015
Grogan says that how women choose to look is their decision alone and that fat-shaming, is unacceptable.
"Having this choice in clothing and allowing women to build their confidence by finding themselves and their style can then mean that women are confident enough to make their own decisions on their body image and only change it if they truly want to."
Jamelia stood by her statement during an appearance on This Morning on Wednesday 22 April.
"Knowing I offended people really upset me," she said. "But I do stand by what I said - I am a real women with real opinions... I get paid to voice my opinion. Occasionally you offend people."
She added that she had ben talking about "extremes", which she explained meant people "above a size 20 and below a size 6."
Debz was so outraged by Jamelia's remarks she decided to write an open letter to the former popstar on her blog:
"If you think that the fact someone wears clothing a couple of sizes 'too big' makes them the right kind of victim to shame and bully then your position as a TV presenter makes me sad.
"You speak to a nation of people every lunch time and you have the power to do such good. Today you choose to tell people that fat people should be made to feel uncomfortable when they are clothes shopping - what type of person does that?"
Debz says she was amazed by the response her open letter received and that inspired her to start the #WeAreTheThey Campaign.
"The hashtag #WeAreThe They was created after my original open letter to Jamelia got such a good response," Debz tells HuffPost UK Lifestyle.
"I realised she had touched a nerve with people who usually wouldn't speak out about this type of bullying.
"I wanted to show Jamelia that although it is easy to say 'they should be made to feel uncomfortable' she is referring to real people and having an effect on real lives."
— Debz (@Debzjs) April 22, 2015
"Even today people are using the hashtag to show off their photos and I hope they continue to do so," adds Debz.
"It goes to show that together we are strong and something like this was definitely needed. I'll continue to strive for body positivity on my blog and now it seems others will too!"
Scroll down to see some of the photos that have been shared already...
— Danielle (@VanierDanielle) April 22, 2015
— Apple Writer (@applewriter) April 22, 2015
— Nick Gregory (@Nickipedia101) April 22, 2015
— Kelsey Shepherd (@KelseyShepherd_) April 22, 2015
— Mayah (@MayahThomas) April 22, 2015
— Bettie (@bettieriot) April 22, 2015
— Naomi Griffiths (@Naomi_Griffiths) April 22, 2015
— Katie Pennick (@KatiePennick) April 23, 2015
— Hannah (@Fabfatfashion) April 22, 2015
— Charlotte (@AppleCharlotte) April 22, 2015