Bababing, a child and baby products company, claimed the bag sold by the budget supermarket chain has “identical” features to one of its own designs.
The Mani Mani Backpack Changing Bag, which retails at £49.99, was first launched on the Bababing website in 2018.
Aldi’s bag, meanwhile, launched in January this year as part of a week-long baby promotion.
The lookalike product retailed at just £17.99.
Nick Robinson, managing technical director at BabaBing, told the BBC: "It's no coincidence, the number of features that are identical to ours - it's not them designing a bag.
"In my view they've taken our bag and blatantly copied it."
"They're not overpriced, they're very competitively priced and the quality is far better than Aldi."
Speaking about the alleged copying on Twitter, a representative for Bababing said such incidents represented a “threat to small businesses”.
An Aldi spokesperson told Yahoo UK: “At Aldi we aim to provide our customers with products of a similar high quality to the leading brands, but at a fraction of the price.
“We sell a wide range of baby products that are hugely popular with parents and we will consider Mr Robinson’s views when planning future ranges. We always listen to feedback on our products and would be pleased to meet with Mr Robinson to discuss his concerns.”
This isn’t the first time Aldi has landed itself in hot water with customers recently.
In January of this year, it was called out for selling so-called “flexitarian” burgers – which contained meat.