Luxury fashion designer Karl Lagerfeld is facing a multi-million dollar lawsuit from New Balance after allegedly copying the sports apparel manufacturing giant's signature block capital 'N'.

In the court documents obtained by TMZ, the athletic shoe brand, who has been using the design since the 70's, claims the Chanel style icon is creating confusion for its customers. Lagerfeld is using a block capital letter 'K' on a pair of his sneakers.

It also asserts that even fashion blogs have noticed the similarity - with one writing: "Wait did Karl Lagerfeld just knock off New Balance sneakers?"

While you can pick up a pair of New Balance' iconic trainers for $120 (£72), Lagerfeld's will set you back triple that amount at $360.

Although it is not clear if Lagerfeld was inspired by New Balance trainers, trademark experts say it will be difficult to prove infringement.

"A logo is a walk in the park. Trying to establish ownership of a design is more like climbing Mount Everest. A logo, a name, a symbol that you use on every item of clothing or every accessory is registered with the trademark registration office and just as long as it doesn't look too closely like everyone else, it's a pretty simple process," Lordham School of Law's Susan Scafidi told Style Caster.

"Trying to own the actual design of a bag or a dress means having to prove to the trademark office secondary meaning. That means that you have to show that when a consumer looks at that bag—say it's a Birkin—and automatically say, 'Oh! That's a Birkin.'"

Famously opinionated Lagerfeld has not commented on the infringement claims.

New Balance
Spot the Difference: The New Balance trainers with the signature N (Left and Lagerfeld\'s new trainers on the left.