The New York attorney general says that while Secretary of State Rex Tillerson was CEO of Irving-based Exxon he used an alias in emails to talk about climate change.
The attorney general, Eric Schneiderman, made the accusation in a letter from his office to a New York court Monday.
He is investigating whether the company deceived investors and the public by hiding for decades what it knew about the link between fossil fuels and climate change.
Schneiderman said Exxon failed to disclose that Tillerson used an account named "Wayne Tracker" to send and receive emails about issues including risk management related to climate change. Wayne is Tillerson's middle name.
The account was used from at least 2008 through 2015, he says.
Exxon Mobil spokesman Alan Jeffers said Tillerson's regular email address received a large number of emails, including from outside the company, and the Wayne Tracker account was created for secure and quick communication between Tillerson and senior executives over a broad range of topics.
Tillerson resigned as chairman and CEO of Exxon Mobil Corp. at year end, after then-President-elect Donald Trump picked him to become the nation's chief diplomat.
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The State Department declined to comment on Tillerson's use of an alias for email while at Exxon, but spokesman Mark Toner said Tillerson only uses a State Department email address to conduct government business and an official phone number for work-related calls.
In a letter submitted by one of his deputies, Schneiderman said investigators found the Wayne Tracker account on about 60 documents but that neither Exxon nor its lawyers ever disclosed that it was used by Tillerson. He said that Exxon has failed to give his office all documents covered by a court order in response to his investigation.
Exxon disputed this.
"The very fact the attorney general's office has these emails is because they were produced in response to the subpoena," Jeffers said in a statement.
He said the company has provided more than 2.5 million pages of documents to Schneiderman's office.
Tillerson would not be the first chief executive to use an alias in electronic communications.
A notable case was John Mackey, the CEO of Whole Foods Market Inc., who used a pseudonym to post messages on investor websites criticizing another company and suggesting that its stock was overpriced.
Austin-based Whole Foods later bought the rival over objections by federal antitrust regulators.