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.

The SEC usually follows a Wells notice with a formal complaint, although it may reduce the number of charges after hearing from the target’s lawyers. In rare cases, the commission opts not to press forward. The SEC declined to comment.

In its 2009 annual report, ICAP said the SEC investigation involved other interdealer brokers in government and other fixed-income securities.

The SEC issued a formal order of investigation into ICAP’s subsidiary in February 2006. The regulator has “issued several requests” for information relating to the unit’s voice-brokered mortgage-backed securities desk, according to the annual report. That aspect of the probe has been in progress since April 2008.

“There are no issues which are currently expected to have a material adverse financial impact on the group’s results or net assets,” ICAP said in the report. ICAP’s US activities are primarily regulated by the SEC and Finra, a self-regulatory body that oversees broker dealers.

The SEC enforcement division has been pushing to finish high-profile cases under its new leadership in New York and in Washington, after criticism of its oversight activities during the financial crisis.

(Financial Times: By Joanna Chung in New York)