Online fashion retailer Asos saw a sales increase of 86 per cent during the Christmas season, with annual profit before tax set to exceed expectations.

"We had a cracking Christmas," said chief executive Nick Robertson.

"Sales were ahead of internal forecasts, margin remained strong and our stock position healthy."

Physical processes such as logistics pose a challenge for most retailers with a web presence, but Asos experienced no major delivery issues in the run up to Christmas, according to Robertson.

The site has 1.7 million registered users.