There has been a dramatic rise in securities litigation in the US this year, with more than half the lawsuits relating to initial public offerings (IPOs), according to PricewaterhouseCoopers, the professional services firm.

A record number of 263 federal class actions have been filed this year with 143 cases relating to IPOs that name the underwriters and companies as defendants. The cases filed so far this year are already a 31% increase on the 201 class action lawsuits in the whole of last year and the 207 cases in 1999.