The chairman of a powerful US congressional committee is scrutinising Diligence LLC, an international investigative agency chaired by Michael Howard, the former head of the Conservative party, over allegations that the company engaged in corporate espionage.

Henry Waxman, chair of the main House investigative committee, sent a let-ter this week to a -Chi-cago-based attorney for Ipoc International Growth Fund, a Bermuda group that has filed a lawsuit in the US against Diligence and -Bar-bour, Griffith & Rogers, a Washington lobby firm. The firms are accused of -per-petrating a "vast international scheme" to misappropriate millions of dollars from Ipoc.