In a week that Nikola Corporation’s founder Trevor Milton would probably prefer to forget, further allegations have surfaced regarding Milton and the company’s claims on designs and technology for its hydrogen fuel cell trucks.

Reports in The Financial Times claim Milton purchased the original design for Nikola’s flagship truck from a Croatia-based designer, with the story citing insiders with knowledge of the matter.

It follows a week which saw Milton resign as chair of Nikola over allegations made by Hindenberg Research about the origin of the designs of critical technology and also the validity of video footage of test trucks moving under their own power. It also came in a week that would have seen Milton and Nikola sharing centre stage with its European truck partner and investor, Iveco at the Hanover Truck Show, which has been cancelled due to Covid

The Financial Times report says the flaghip Nikola One is at the centre of a design patent infringements lawsuit that Nikola filed against Tesla in 2018.

Nikola claims that Tesla’s Semi truck, the first electric heavy duty truck from the Elon Musk company, was “substantially” similar to Nikola’s design.

The FT report cites people with knowledge of the deal and alleged that Milton purchased the designs of the vehicle for several thousand dollars from Rimac Automobili’s designer Adriano Mudri in 2015.

“The Nikola One truck was designed and patented by Nikola,” Nikola said in a statement.

“It is commonplace to license third party designs during vehicle development, and although early in the process Nikola purchased a license to Adriano Mudri’s designs, he was not part of the design team and his designs are materially different from the design invented by Nikola for the Nikola One,” the Nikola statement concluded.

The FT report comes after Tesla denied the design patent infringement charges in a filing, saying that Adriano Mudri was the designer of the hydrogen-powered concept truck, dubbed “Road Runner”, and Milton was aware of the concept before filing design patent application.

Tesla and Rimac Automobili were not immediately available to a request for comment.

In the scathing report, Hindenburg Research, a company which admits it is a market “short-seller”, said it had enough evidence to show Nikola and its founder Trevor Milton had made false claims about the company’s proprietary technology to enable it to form partnerships with automakers, a factor which triggered Milton stepping down as chair.

Nikola, says it is discussing the claims with the U.S. Securities and Exchange Commission and has publicly rejected the accusations, threatening to take legal action against Hindenburg.