Asos is clearly viewed as a channel for its competitors to expand their global reach, according to a retail analyst.
Topshop and Topman are set to launch ranges on rival Asos' website in the next few months.
GlobalData senior retail analyst Sofie Willmott said the move is a substantial one for Asos.
“Despite Arcadia’s long term sales slump, it is a coup for Asos to have secured two of its challengers in the youth fashion market and demonstrates its position as a retail powerhouse.
"With H&M’s in demand yet sparsely available brand, & Other Stories, launching earlier in May, Asos is clearly viewed as a channel for its competitors to expand their global reach.
“Moving to where shoppers are makes sense for Topshop/Topman whose sister brands, Miss Selfridge and Burton already sell on the site, with products available in abundance."
Willmott warned brands to consider the risk versus reward.
"Ranges must be edited to ensure consumers still have a reason to visit the individual brands’ websites.
"Topshop/Topman need to launch with strong ranges to protect their brand identities and longevity, but also to compete with the plethora of other fashion players that sell on Asos including boohoo.com, River Island and Missguided.
“Arcadia has pledged to invest £60m to upgrade its online operations which is much needed as it will now be even more important that the brands’ websites stand up to Asos’ best in class proposition.
The online giant’s appealing Premier delivery saver scheme encourages shoppers to make the online pureplay their first port of call for a fashion fix; and for Topshop/Topman to drive conversion on their own sites, fulfilment options must be just as fast and affordable."
Willmott said market leading technology will also influence the partnership.
“Similarly, Asos’ nifty tools such as visual search and boards where you can pin products, drive repeat visits so the Arcadia brands must introduce equivalent functionality to satisfy young shoppers with high expectations.
"However, given Asos is a tech-focused retailer that prioritises frequent small tweaks to its proposition, alongside major enhancements, to constantly improve the shopping journey, it is difficult to see how Arcadia, as a multichannel player, will be able evolve quickly enough to match the rapid pace set by its new partner."