Some seemingly ordinary people are getting paid thousands of pounds to post on Instagram, the photo-sharing app. But are these Insta-celebs just publicity-seeking pouters, or is posting a credible – and ethical – way to make money?

People of a certain vintage might wonder what we’re talking about, so here’s the basics: Instagram is a social networking app for sharing photos and videos, either on a smartphone or desktop computer. Similar to Facebook or Twitter, users create a profile and post content with captions and hashtags (using the # sign). You can follow other people, see their photos and videos in your newsfeed, and leave comments.

Sara Tasker, a 32-year-old from Yorkshire, set up her account @me_and_orla while on maternity leave four years ago, initially posting a picture a day. She now has about 160,000 followers and has jacked in her job as an NHS speech therapist to work on Instagram full time. And it’s paid off – she earned around £120,000 last year. “I initially posted lifestyle-type pictures – nice moments in my day, like a slice of cake or flowers on the windowsill,” she says. “I noticed other people were getting free products or payments from brands and thought ‘I want some of that’.”

I noticed people were getting free products or payments from brands so thought: ‘I want some of that’ Sara Tasker

Tasker initially traded product mentions for freebies, but now charges companies for appearing in her Instagram feed. She’s worked with Boden, Canon, Ikea, Land Rover, Citroën, Garnier and Boots No 7 among others. “I’m picky about who I work with,” she says. “Authenticity is a buzzword in Instagram and you need to find a balance between staying authentic and making money. Branded work means I have more time to post ‘real moments’, but I only work with brands in line with my values.”

Tasker is what is known as a “micro influencer” – a non-celebrity who’s built a decent social media following by creating and sharing popular content.

While many of the top-earning accounts are full of celebrities, ripped hunks and bikini models, they’re not all like that. Some Instagrammers aim to educate and create a community around a certain subject.

Jenna Farmer, 31, from Warwickshire, is a qualified nutritional therapist and a freelance nutrition writer. She runs a blog called abalancedbelly.co.uk and the @abalancedbelly Instagram account, both about the non-sexy subject of inflammatory bowel disease. Despite having a relatively small following of around 2,800, she’s regularly asked to review restaurants or mention food products or supplements.

“I post quite regularly but my area is quite niche – Crohn’s disease. My posts are food-related and about gluten and dairy-free foods,” she explains. “I’m selective about who I work with. Many food supplements don’t live up to their claims so I won’t promote them. For a package of Instagram, a blog post and a tweet I’d normally charge £200-£300. Some brands just want a mention on Instagram, for which I’d charge £50-£100. I probably earn £100-£200 a month from Instagram and £500-£700 a month from my blog.”

To their audiences, micro influencers are seen as knowledgeable, passionate, authentic, and viewed as a trusted source of product recommendations. To companies and brands they are a way to reach a wider audience. Paying influencers to plug or picture products is known as “influencer marketing”. How much cash changes hands depends on how many followers the influencer has, the level of “engagement” (comments and likes) their posts typically get, and their negotiation skills.

Estelle Puleston runs Instagram campaigns for influencer marketing agency CollectivEdge.com. “When you have a few thousand followers, you’re mostly likely to be offered product-for-post collaborations rather than money,” she explains. “At the opposite end you’ve got your Kim Kardashians paid tens of thousands of pounds per photo, but for your in-the-middle, non-celebrity influencer it will be significantly less.”

Perhaps, inevitably, a whole industry has sprung up connecting brands and influencers. Apps and platforms with catchy names such as Tribe, Takumi, Indahash, Buzzoole, Snapfluence and Instabrand help users with a significant following (usually at least 1,000) connect with brands and monetise their account. Feeds which cover lifestyle topics such as fashion, beauty, fitness, food and travel tend to be popular.

Snap: a Kim Kardashian on Instagram. Photograph: @kimkardashian/instagram

A report by Takumi last year found that influencers with a minimum of 1,000 followers can earn about £40 a post for a brand. Someone with more than 5,000 followers could charge roughly £75, while an influencer with upwards of 20,000 could charge £300 or more. There’s anecdotal evidence of some Instagrammers raking it in. Take Jack Morris and his girlfriend Lauren Bullen: the photogenic 20-somethings reportedly earn a six-figure salary from their travel-focused @doyoutravel Instagram feed, which has 2.4 million followers.

Australian model Gabrielle Epstein has 1.8 million and has boasted that a selfie a day can earn her more than four days’ work. Her recent posts have promoted sportswear company Women’s Best, clothing brand Tezenis, and Miola bikinis. Each post attracted between 28,000 and 63,000 “likes”.

“It can seem like a lot of money for not a whole lot of work, but the real work … is in cultivating a large, engaged audience that makes brands want to feature on your feed in the first place,” says Puleston.

Magazine editor-turned blogger Alison Perry runs the Not Another Mummy Blog and joined Instagram in 2011. Her account @iamalisonperry has around 12,700 followers and generates an income. The past couple of years have seen her improve her photography skills, invest in equipment, learn how to edit photos and work out a theme to her feed.

“It might sound ridiculous to someone who doesn’t use Instagram much, but I put an incredible amount of time thinking up concepts of photos, taking photos, editing photos, planning which photo to publish next (I use an app to help me do that), writing the captions and working out which time of day to post – after all, you want your photo to be seen by as many of your followers as possible,” she says.

Follow the rules or it can backFyre

Instagram posts can easily backfire, writes Patrick Collinson. The disastrous Fyre festival recruited hundreds of online personalities to advertise the event with social media promotions that did not disclose they were part of a marketing campaign. The festival, billed as a luxury Bahamas getaway for the wealthy, descended into chaos and lacked basic, functioning amenities. It was promoted by more than 400 “influencers” with huge social media followings.

Misleading: Fyre festival’s luxury toilets. Photograph: AP

Instagrammers who are paid to promote products, and where the message is controlled by the brand, are subject to the same rules around advertising as any other media. In other words, the message should not mislead, harm or offend, and should be responsible.

“Another key rule that applies, particularly in this space, is ensuring that advertising is ‘obviously identifiable’. We [consumers/followers/viewers] should be aware that the content we see, hear and interact with, is advertising,” says the Advertising Standards Authority. “They shouldn’t have to play detective to work out when it is advertising.”

In December, the ASA ruled against Sheikbeauty who posted “@flattummytea 20% off guys!!!! If you’ve been following me you’ll know I used this and I genuinely feel less bloated and a flatter tummy ... oh yessss”. In the absence of a clear identifier, such as “#ad”, the ASA ruled it had breached its codes.

Callum McCahon, strategy director at social media agency Born Social, says it’s a fundamental ethical issue. “The majority of the time it isn’t clear whether an influencer is being paid, or whether it’s a genuine, organic recommendation,” he says. “The accepted standard is to use a hashtag – #ad, #sp, or #sponsored. But recent research has revealed that 77% of Instagram users in the UK don’t know what #sp means, while 48% don’t know what #ad means.”