Fake Back to the Future trainers already on sale

Counterfeiters have jumped the gun on Nike's forthcoming launch of its Back to the Future themed trainers.

The official version of the self-lacing sneakers made famous by Michael J Fox's character Marty McFly in the 1985 film are not due in stores until next spring, but knock-offs are already popping up on the Internet, according to a TechTimes report.

The genuine shoes - which feature a green button to tighten the laces and a red to loosen them - will only be available via auction. All proceeds are going to the Michael J Fox Foundation for Parkinson's Research, so the availability of counterfeits is particularly iniquitous.

The first pair of the genuine article has already been donated to the actor. "Although the project started as science fiction, we're now proud to turn that fiction into fact," said Nike's Tinker Hatfield, who designed the shoes.

The letter I received from Tinker today. Thanks @Nike pic.twitter.com/UIolXrkUVC

— Michael J. Fox (@realmikefox) October 21, 2015