Brands promoting their products online are quietly deploying AI-generated influencers on social media, an investigation has found, prompting calls for greater transparency.

The findings suggest companies are increasingly turning to AI-generated content that purports to show genuine customer experiences while giving no obvious indication that the people featured are not real.

The Guardian has also found that some content creators making AI influencer content are being asked to sign non-disclosure agreements so they cannot talk about their work.

There are no specific rules requiring brands to tell consumers when advertising content has been created using AI. In the EU, new rules under the Artificial Intelligence Act will begin applying in August, requiring AI-generated or manipulated content such as deepfake images, audio and video to be clearly labelled. The legislation will not apply in the UK.

The consumer group Which? said that customers should be clearly informed when promotional content features AI-generated influencers rather than real people.

One example of a business appearing to use this content on Instagram includes a photo app called Once, which allows people’s phones to create disposable camera-style photographs for events. According to analysis by Reality Defenders, a cybersecurity company specialising in deepfake detection, the brand has likely used AI-generated influencers in its promotion.

Several videos on Instagram show a bride crying and saying she was pleased to have used the Once app at her wedding. In one she says: “Everyone expected a no-phone wedding, so I gave them cameras instead.” The post was captioned, “The app I used is called @oncefilmapp.”

When asked about this, Once did not respond to a request for a comment.

In another video a woman who appears to be AI generated says in a caption on the screen: “I could kiss the interior designer who showed me this.” She then goes on to show herself using the Maket app, which uses AI to design and plan housing projects.

Maket said: “AI-generated influencers have been one of several ways for us to test creative concepts and marketing hooks at a small scale before investing in broader campaigns. This is not a core part of our marketing strategy, but rather an experiment to better understand what resonates with audiences across channels, including influencer, social media and email campaigns.”

A fashion brand called Ashle, a Dubai-based business, posted a photograph appearing to show a woman wearing its clothes at a restaurant. The woman appears to have an extra finger. After being approached by the Guardian to ask about the use of AI influencers, the brand deleted photographs from its social media page.

A spokesperson for Ashle said: “To clarify, all Ashle pieces are real garments that are handmade to order. We are not selling AI-generated products. Some early marketing imagery utilised AI during our initial launch phase to showcase designs.

“The images that have been removed were taken down because those particular designs are no longer part of the collection, not because they were AI-generated.”

Lisa Barber, editor of Which? Tech, said: “Our recent investigation into deepfakes on social media found that a worrying 70% of people are unable to correctly identify all the real and fake videos we showed them, meaning consumers could be frequently being misled by AI-generated content and becoming targets for scammers.

“It is concerning that consumers are not able to trust the content they are seeing online. Companies must be transparent when content has been created using AI, particularly if AI-generated influencers are appearing in the content.”

The Advertising Standards Authority (ASA) said there was nothing in its rules that explicitly prohibits brands from posting AI-generated promotional content without disclosing it.

“There’s nothing in our rules that prohibits this and there are no disclosure rules for AI content labelling,” an ASA spokesperson said. “The content would, of course, still need to stick to the advertising rules. For example, it mustn’t be misleading and it must be socially responsible.”

The regulator said the use of AI itself is not the issue it would assess when considering complaints.

“That would depend on whether the use of AI results in the consumer being given a misleading impression of the product being advertised,” the spokesperson said. “Ultimately, the issue we would look at is whether the ad itself is misleading, rather than the use of AI being inherently problematic.”

Clarissa Mansbridge, a former celebrity manager who has previously worked with Katie Price, creates images of AI influencers for brands as part of her Mia Metaverse portfolio. She says brands approach her because she has the technical ability to create hyperrealistic, aspirational digital humans.

Brands can hire Mansbridge to create entirely new AI avatars that are used for user-generated content (UGC) – a form of content paid for by brands where humans review their products. For example, a beauty company may commission a realistic-looking video of an anonymous 20-year-old applying sunscreen beside a pool in Bali. The brand can then post the content directly on its own social channels, making it appear as though it was submitted by a real influencer.

“I’m going to say about 40% to 60% of the content out there from some of the big brands is actually being made through AI, but a lot of the creators are under NDA,” Mansbridge said.

“If you sign with a brand, they’ll make you sign an NDA saying you can’t talk about the fact they’re using [AI], because consumer trust is still being built. I call it plausible deniability.”

Mansbridge said brands are increasingly attracted by the lower costs associated with AI-generated content.

“Brands want high-end photography, but they don’t want to pay $20,000 to $70,000 for a traditional photoshoot,” she said. “Unfortunately, human influencers killed the market for themselves. Brands are moving to AI to cut out issues like bad press, personal opinions, hourly rates and photographers.”

Mansbridge said the paid “UGC boom” started around three years ago, “when influencers were incredibly smart about it. They noticed brands were desperate for content that looked like real, everyday people using their products, so they started pitching paid content framed in that style. Brands loved it and paid for it.”

She added: “The authenticity of UGC was always about resonance, not [about] who made it. If the content reflects a real consumer truth about the product, it connects. AI just gives brands a smarter, more scalable way to get there.”

The use of AI-generated content that mimics authentic customer experiences is also being actively marketed to businesses.

Leeds-based artist Zac Rossiter said he was recently approached by a marketing agency promising to help boost sales. In an email seen by the Guardian, the agency wrote: “Pick one of your products. I’m thinking your artwork prints, but it’s up to you. We will use our AI studio to generate you a complimentary piece of ad creative for it, yours to keep.”

The agency said it wanted to create an AI-generated unboxing video featuring one of Rossiter’s products. Unboxing videos, in which customers open and react to products on camera, have become a popular form of user-generated content because they are often viewed by consumers as authentic recommendations.

Rossiter declined the offer. “I would never work with an agency that used fake AI unboxing videos over actual, real people,” he said.