The founder of Trunki suitcases has predicted "chaos" after his company lost a court battle with a rival over product design.
Magmatic - which sells the children's ride-on cases decorated to look like animals or insects - lost out in a Supreme Court ruling.
The court said PMS International's Kiddee Case range didn't infringe registered design rights.
Rob Law, creator and CEO of Trunki, tweeted he was "devastated".
He added he was "bewildered by this judgment, not just for ourselves but for the huge wave of uncertainty it brings to designers in Britain".
The design battle had already gone through the High Court, which backed Bristol-based Magmatic, and the Court of Appeal, which supported PMS International.
In its ruling on Wednesday, the Supreme Court backed the Court of Appeal.
Supreme Court Justice Lord Neuberger said Trunki was "both original and clever" and he said it "appears clear" the Kiddee Case had been conceived "as a result of seeing a Trunki and discovering that a discount model was not available".
But he said: "Unfortunately for Magmatic, however, this appeal is not concerned with an idea or an invention, but with a design."
The court said design law was based on the "overall impression created by a design", which in Trunki's case was "an animal with horns".
It said this was "significantly different from the impression made by the Kiddee Case, which were either an insect with antennae or an animal with ears".
But Mr Law tweeted: "The law is meant to be about certainty. But this decision will create chaos and confusion among Britain's design community".
Magmatic registered its ride-on suitcase design in October 2003 as six computer-generated images.
Business leaders and celebrities were among those to support the rights of British business as the Trunki case moved through the courts.
The #ProtectYourDesign Twitter campaign was launched by Trunki with the aim of getting "more robust protection" for designers
It gathered the support of the likes of Habitat founder Sir Terence Conran, Grand Designs presenter Kevin McCloud, Brompton Bikes boss Will Butler-Adams and Innocent Drinks co-founder Adam Balon.
Trunki said: "This battle has been hugely draining for us, both financially and emotionally. But It's no longer just a fight to protect Trunki."
It added: "Under this ruling the rights of more than 350,000 creative British businesses would be undermined and designers left vulnerable to flagrant design infringement."
In 2006 Mr Law appeared on BBC Two show Dragons' Den in 2006, unsuccessfully seeking investment for his Trunki case.
After he was rejected by the Dragons, he went on to sell more than two million of the suitcases in more than 60 countries.
Lawyer Mike Gardner, a partner at law firm Wedlake Bell, said the case showed how difficult it could be for businesses when design law protected the appearance of products rather than ideas.
He said: "Magmatic's registered design showed computer-aided drawings of the Trunki which included some shading and dark colours for the wheels.
"These had to be taken as part of the design and not ignored as Magmatic contended."
But Michael Moore, partner at intellectual property law firm Marks & Clerk, said judges had to "strike a balance between fair protection and free competition".