Financial firms operating in the United Kingdom will have to start recording staff mobile phone calls under new regulations from the industry regulator. The move is an effort to limit insider trading.

The Financial Services Authority made an exemption for cell calls when it told firms to record phone conversations in March 2008, but it has now decided to include such calls in its rules.

Beginning November of next year firms will have to record and store for six months any “relevant communications made with, sent from, or received on mobile phones and other hand-held electronic communication devices.”

A relevant communication is one where an employee discusses receiving, executing, or arranging client orders for securities trading. It doesn’t apply to corporate finance business or corporate treasury functions.

The rule will only apply to phones and devices that firms give their staff for business purposes. But the FSA said firms must ensure that staff do not discuss relevant issues on their private cell phones.

Firms will also have to record calls that staff make when overseas, if they frequently use their phone for deal calls when traveling, unless local laws prohibit the recording.

The regulators predicts that the rule change would require the monitoring of 16,000 mobile phones.