Waterloo Sunrise said:
I find this hard to believe - It is 100% illegal for any of a supermarket's suppliers to dictate a price - even packs with prices listed on them have to be done 100% at the supermarket's request lest they break that law.
It seems unlikely that practice doesn't apply to clothing sales.
best believe it then.

Last year Adidas supplied the kit to about 20 re-sellers, and there was a set retail price which the retailers where allowed to discount 10% off at most. Some did this as a "webprice" some as an incentivised purchase.
we dealt with one retailer in 2010 who publicly offered x % and was able to do us y % discount but it was a private code offered only by us via email and as a result we had the cheapest UK prices for Sky kit for the whole of 2010. That supplier no longer stocks adidas team Sky products, in fact the authorised distributor list for this year in the uk has dropped to about 8 retailers.
At the start of this year we recontacted all the retailers to try and establish a deal for this season (basically a free ad on the site offering an additional discount using the link - with us recieving no comission.) all the responding retailers said that anything had to be approved by adidas so we approached them and were informed that they could not grant any additional discounts through any authorised retailers.
Adidas kit is price set. Which is why this season we have no advertising on the site for the team kit.
I thought carefully before posting this as Its a fairly serious allegation but in the end, I know, that its accurate. Its not price fixing in that they only allow authorised retailers to sell the kit and encourage them to sell it at price x. They can sell it cheaper, but of course then they wont get supplied.
And yes, the law also applies to clothing sales. There have already been big court cases involving JJB and other retailers in regards football kits.