German sportswear maker Adidas has decided to allow the sale of its products via market-place sites like eBay and Amazon, an issue the German cartel office has been investigating.

"We have decided to extend our e-commerce guidelines to also include open market places: if our retail partners adhere to our criteria, there will be no restriction for online sales in any channel," Adidas said in a statement on Tuesday.

Adidas had previously said it wanted its products to be sold only via expert and specialist retailers rather than eBay and Amazon to ensure they were presented "in the best possible way and in the right environment".

Adidas said on Tuesday it had made the change because the functionality of e-commerce distribution channels had improved as the market had evolved.

A spokesman for the German cartel office, which in April expressed concern over similar restrictions imposed by rival sportswear firm Asics Corp, said on Tuesday it was close to concluding an investigation into Adidas.

The Cartel Office, which is still investigating Asics, has said the ban of the sale of its products via market-place sites amounts to a way of limiting price competition.