The US Securities and Exchange Commission has warned ICAP, the world’s largest interdealer broker, that it is considering filing securities fraud charges against one of its US subsidiaries.

ICAP said on Friday that ICAP Securities USA LLC had received a so-called Wells notice from the SEC’s New York regional office, warning that the enforcement staff was strongly considering filing civil charges. The notice related to an existing SEC investigation into the market in certain fixed-income securities, which opened in 2005.