Kylie and Kendall Jenner are amongst dozens of influencers BBC Click has discovered to be promoting the sale of imitation Apple AirPods on Instagram.
The two celebrities have a combined following of 322 million followers.
Apple says cloned earphones infringe its intellectual property rights. It is not thought to be pursuing a case against the two sisters.
However, the firm has taken previous action against influencers it believed to be hawking "knock-off" AirPods.
Kylie and Kendall Jenner declined to comment.
Click's investigation uncovered dozens of social media influencers promoting clones of Apple Airpods and Apple Watches.
The influencers do not hold stock of the goods themselves. Instead, they promote links to websites where anonymous sellers ship the products directly from China.
The products typically may be indistinguishable from the genuine items at first glance but feature different brand names on their packaging and sometimes deliver a poor user experience.
Promotion of such products can be regarded as being a copyright and trademark infringement under UK law, if the knock-offs are deemed to look similar enough to the legitimate items.
The national co-ordinator for the UK's National Trading Standards eCrime team said that if influencers were found to be promoting knock-off products, in the first instance they would be informed of consumer laws, but if they continued then "formal action" would be considered.
"We would be concerned that some consumers, swayed by the power of social influencers, and the overall look and feel of the websites, might be misled into thinking they are buying genuine Apple AirPods," Mike Andrews said.
Instagram itself has told the BBC that influencers must follow local laws and vet brands before agreeing to paid partnerships.
The vendors behind the products are known as drop shippers - a kind of intermediary who doesn't make or even see the products they sell, and uses influencers to promote them.
They typically source their products from online Chinese marketplaces and have them sent directly to consumers.
'You can have a massive business without ever going to China," Kevin David, a drop shipper based in Miami told Click.
"I've personally sent millions of dollars to China. I've gotten millions and millions of dollars of products and I've never even been to China."
He added: "Those Airpods, some of my personal friends make hundreds of thousands a month selling those."
While legal, drop shipping is open to abuse with reports of:
products not being delivered
refunds not being given
websites suddenly being shut down
"All you need is an internet connection and a website and you're ready to go," commented Sanchit Jain, an e-commerce analyst, from the consultancy Ender Analysis.
"The downside is that people get conned, don't get what they paid for and are misled. It really is the Wild West, especially because you are easily able to create a new store as and when you please."
Apple told BBC it was aware that drop shipping contributed to counterfeit sales and allowed bad actors to remain anonymous.
It added that its teams "are continually adapting to counterfeiters' latest tactics".