Shares in Tullett Prebon fell more than 12 per cent after the inter-dealer broker revealed that recent staff defections to rival BGC Partners on its North American dealing desks had led to a 9 per cent fall in revenue between July and October.

The disclosure highlights how vulnerable the inter-dealer broking business remains to broker poaching, a practice described by Mickey Gooch, chief executive of GFI, another inter-dealer broker, as “a circular firing squad” that was damaging the business.