The chief executive of US retailer Whole Foods Market has defended his past attacks on takeover target Wild Oats Markets as “playing devil’s advocate”.

John Mackey has been outed as “rahodeb”, an anonymous member of Internet financial forums, who from 1999 to 2006 claimed that Wild Oats’ shares were over-priced and speculated about the company’s future prospects.

The revelation is something of an embarrassment to Mackey and Whole Foods. The company is in the middle of a legal battle with the Federal Trade Commission, the US competition watchdog, over its planned merger with Wild Oats, a rival retailer of natural and organic products.

The FTC is trying to block the merger on anti-trust grounds, claiming that consumer choice in the natural and organic sector would be undermined if the deal went through.

Furthermore, last month, Mackey took the somewhat unusual step of launching a blog on the Whole Foods’ website to attack the FTC’s stance and promote the benefits of the merger.

Yesterday (11 July), Mackey used the same blog to defend his musings under the pseudonym, “rahodeb”. He said his identity had come to light “through one of the millions of litigation documents that Whole Foods provided to (the FTC)”.

“I posted on Yahoo! under a pseudonym because I had fun doing it. Many people post on bulletin boards using pseudonyms,” Mackey said. The views articulated by rahodeb sometimes represent what I actually believed and sometimes they didn’t. Sometimes I simply played devil’s advocate for the sheer fun of arguing. Anyone who knows me realises that I frequently do this in person, too.

“Rahodeb’s postings therefore do not represent any official beliefs, policies, or intentions by either Whole Foods Market or by me.”

Mackey added that the views of “rahodeb” should be placed in context. “Because the competitive market has evolved so much in the last five years, older postings mean far less today than they did when they were written.”

In a post under the pseudonym from 2001, Mackey said Wild Oats did not have a “sustainable business model”, while its “overall operations execution is weak”.