British spread-betting firm IG Group said it would seek a London listing in May, less than two years after a £143 million management buyout took it private.

A spokesman for the company said it was too early to say how much an initial public offering would raise, but newspaper reports have said a listing could value the firm at more than £375 million.

IG is the biggest UK spread-betting company, allowing investors to speculate on share prices and indexes, currencies and interest rates. It also offers trading in contracts for difference (CFDs) and sports betting.

Industry sources estimate IG has about 30 per cent of the UK market, although no official data on market share is released.

Growth has surged in recent years as investors have used spread betting as a tax-efficient alternative to traditional stock market activity. It also allows them to take a short position to effectively sell stocks they do not own.

IG said that its earnings before interest, exceptional items, taxation, depreciation and amorisation rose 40 per cent to £16.1 million for the six months to end-November, on turnover of £29.5 million.

Competition from rivals - notably City Index, CMC Group, Finspreads and Cantor Index - has intensified in the last year as trading platforms have improved and spreads offered by the firms have tightened.

IG was founded in 1974 by businessman and Conservative Party backer Stuart Wheeler and floated in London in 2000. In July 2003, it was delisted following a management buyout led by Nat le Roux, its chief executive, and backed by private equity firm CVC.