Shares in online trading firm IG Group suffered their biggest one-day fall for a decade after a surprise drop in revenues.

The FTSE 100 company, the world’s first spread-betting firm, said sales in the third quarter were down 14 per cent on a year earlier at £240million.

The London-based company said it now expects full-year revenues to grow in the ‘mid-single-digit’ percentage range, having previously targeted a 10 per cent to 15 per cent expansion.

Underdog’s $105 million third-quarter revenue fell short of the $125 million quarterly run rate it ​averaged in the first half of 2026. IG bought ​the ⁠US prediction markets operator in July this year.

IG now expects 2026 group revenue growth to be in the mid-single-digit percentage range, compared with ⁠the previous ​forecast of 10-15% growth. Third-quarter revenue is ​expected to be about £240 million ($316.97 million), down roughly 14%.