The photograph of them, taken by singer Bryan Adams, shows the panellists without filters or airbrushing.
Ms Street-Porter, 70, said they were "sick of pictures of women being photoshopped into 'perfection'".
Actresses Nadia Sawalha, 52, and Linda Robson, 59, and TV star Katie Price, 38, are among those who took part.
The image will be shown on billboards across the UK.
Presenter Saira Khan, who appeared on The Apprentice, says being Muslim meant she had been "brought up with the mentality to not draw attention to my body".
She added: "I battled against my curves when I was younger as I didn't want boys to notice me for being sexy - I was brought up to never bare my skin in front of men - it took me a long time not to feel guilty for wearing a dress or baring my arms.
"I want to say 'this is NORMAL,' particularly to women of colour. Forget the airbrushed images you see. This is what I REALLY look like. I'm sticking two fingers up."
The women agreed to pose for Bryan Adams only if there was no airbrushing with the campaign slogan "Look, but you can't retouch" emblazoned across the bottom of the image.
Despite the panellists giggling and smiling in the photograph, Ms Street-Porter wrote in the Mail that there was a serious message behind it.
"It's time women started feeling empowered - regardless of whether or not their bodies conform to some spurious notion of perfection," she added.
Ms Street-Porter said she wanted to "fly the flag for older women", and warned all women not to be "brainwashed by the fake images", adding: "Real women look like we do - we all just need to enjoy it more."
Meanwhile, Nadia Sawalha said she was initially "panic stricken" about the idea of the photograph, but it was this attitude that spurred her on to practice what she preaches to her daughters.
"What the hell does it matter what we look like as long as we are smart, brave and kind?"
On being asked to be involved in the project, Bryan Adams said he thought it was an interesting brief.
He added: "They want to be natural, they don't want any retouching, and they want it to be real, and I thought, "OK! that sounds really good!""
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The stars of ITV's Loose Women stripped down to their swimwear to show "normal is perfectly fine", says one of the nine, Janet Street-Porter.