Last Tuesday, Ms Spottiswoode met analysts and institutional investors at a lunch hosted by NatWest Securities and a dinner hosted by Smith New Court. That day the volume of shares traded in British Gas leapt to 13 million, more than double the normal daily amount.
Heavy trading in the shares continued through the week, although the share price did not move significantly.
In January, a similar burst of heavy trading in the wake of a meeting between Smith New Court and Ms Spottiswoode prompted a Stock Exchange inquiry. However, a spokesman for Ofgas insisted that she did not release any price-sensitive information last week.
Selling by a large US shareholder is thought to account for much of the surge. But institutional investors are furious that Ms Spottiswoode chose to speak to brokers only days before the release of a long-awaited consultation document on domestic competition.