New online stores that were opened for business earlier this month by three of the world's biggest fashion's biggest brands have been criticised by a technology analyst as being "inadequate" and may even jeopardise customer loyalty.

Ovum claims the last-minute competitive rush by H&M, Gap and Zara to finally launch online stores has meant the quality has suffered, with the retailers also failing to take the customer experience into account.

"Basic and vital functions such as search have not been included," explains Christine Bardwell, an Ovum senior analyst. "Consumers now expect search functionality. Without it, the retailers are not optimising the sales potential of their online stores.

"Another problem is that all three brands have failed to fully localise their sites. This is about more than just ensuring the correct currency and payment methods are offered. The intricacies of local cultures must also be considered, which all three have failed to do. Zara has not localised address formats and Gap isn't even offering local clothing sizes.

"At this stage of online market maturity, by overlooking items such as this they run the risk of loyal customers defecting to the competition."

Bardwell believes that the retailers have been held back from launching online stores until now partly due to the complexity of managing global fast-fashion supply chains.

She says: "Until now, the risk associated with the cost of fulfilment has been a big enough reason for them to sit back and watch how the online market develops."

According to research by Ovum's sister company Verdict, online sales of clothing and footwear in the UK alone are expected to reach GBP3.2bn in 2010, making it the third biggest online market behind electricals and food and grocery.

Bardwell believes it is this growth that has prompted Gap, Zara and H&M to rush take a slice of the pie, especially as it is predicted to slow between now and 2014.

She adds: "This rush has meant some fundamentally crucial elements to making sales from visitors have been dismissed."