Online fashion retailer ASOS has reported an 18% increase in pre-tax profits in the six months to February 29th, rising to £21m (€26m) on the back of a 24% increase in sales on a constant currency basis to £648.6m.

The London-based company enjoyed its most lucrative festive period on record, at the height of business on the 'discount holidays' of Black Friday and Cyber Monday the site processed up to nine orders per second.

Overall ASOS increased its sales by 21% to £667m in the UK, US and Europe.

After three years trying to tap into the Chinese market ASOS closed its loss-making business there. The division haemorrhaged money, racking up losses of £2.7m during the six months as it failed to gain a foothold competing against local firms such as e-commerce giant Alibaba.

Chief executive Nick Beighton commented on the company's struggles in China, "There are always challenges as a start-up in a country, but there are additional challenges to being a start-up in China," he said.

ASOS has invested heavily in developing its online store and mobile app which has built up a user base of 1.4 billion and now accounts for almost half of the company's sales.