LONDON, United Kingdom — British online fashion retailer Boohoo on Wednesday reported a doubling in annual profit, driven by growth in new customers, and said revenue should rise by about 50 percent in 2017-18 as it benefits from recent acquisitions.

Boohoo, which sells own-brand clothing, shoes and accessories online to a core market of 16-24 year-olds, has been one of the stars of the UK stock market over the last year with its shares rising 280 percent.

The firm and online rivals like ASOS are winning share from traditional high street players, benefiting from the increasing popularity of smartphone e-commerce and their use of social media.

Boohoo made a pre-tax profit of £30.9 million in the year to Feb. 28.

That was ahead of analysts' average forecast of £28.7 million, according to Reuters data, and compared to £15.7 million in 2015-16.

Revenue rose 51 percent to £294.6 million as Boohoo increased its active customer base to 5.2 million, up 29 percent, while international growth, particularly in the United States, exceeded management expectations.

The group acquired PrettyLittleThing in January and the Nasty Gal brand in February.

"Both brands have huge potential and the acquisitions represent a step change in the size, structure and operation of the group," said Mahmud Kamani and Carol Kane, Boohoo's joint chief executives.

They said the group had made "a promising start" to the 2017-18 year, forecasting revenue growth approaching 50 percent, including growth from the acquisitions, and a profit margin of 10 percent.

Boohoo floated at 50 pence a share in 2014 but the stock was hammered by a profit warning the following year. Its shares have since recovered very strongly, closing Tuesday at 189.75 pence, valuing the business at £2.1 billion — more than treble the value of UK department store chain Debenhams.

By James Davey; editor: Kate Holton.