Shares in MySale, the online fashion sales site backed by tycoons Sir Philip Green and Mike Ashley, slumped by almost half after a profits warning today.

The site, which launched in Australia in 2007, reported flat revenues for its Australia and New Zealand markets in the five months to November 30, leaving profits for the year to June "materially below market expectations."

Topshop owner Sir Philip and Sports Direct and Newcastle United owner Mike Ashley bought into the business at around its summer flotation on the London stock market and now sit on paper losses amounting to millions.

Sir Philip owns around a fifth of the business and Mr Ashley has around 5%.

Since the site floated at 226p in June its shares have slumped by 61%, giving the business a market value of £135 million.

The site said that competition and a weakened economic outlook in Australia and New Zealand meant that it expected sales in the region to be flat compared to a year ago.

This has offset sales in the UK, which are trading ahead of expectations, and in Asia where revenues were 29% up year-on-year.

It added that since its June flotation it has launched in four new markets, including the UK and US, meaning that it now operates in 10 countries.

The group added that it acquired 3.1 million new members in the year to date, bringing it to a total of 15.5 million with customers downloading almost 4 million apps.

MySale is run by Rutland-born brothers Jamie and Carl Jackson who founded the firm seven years ago in Sydney.

The company, which employs 500 staff, has agreements with over 2,500 brands and retailers who sell surplus or out-of-season stock on its websites.