John Mackey, the man who opened Britain’s biggest organic health food shop in Kensington last month, used an alias to make anonymous postings on a Yahoo! forum defending Whole Foods, the retail chain he co-founded, and criticising Wild Oats Markets, a rival he has agreed to buy.

Mr Mackey, 53. who co-founded Whole Foods in 1980 as a company embodying ethical values, used the name “Rahodeb” to make numerous filings for eight years until last August.

The revelations appear in filings from the Federal Trade Commission, which is investigating Whole Foods’s $565 million takeover of Wild Oats, which was agreed this year.

Rahodeb’s filings, on a stock market forum, included one posted in January 2005 asking: “Would Whole Foods buy OATs? Almost surely not at current prices. What would they gain?” according to The Wall Street Journal, which first reported the filing.

Rahodeb speculated that Wild Oats eventually would be sold after sliding into bankruptcy or when the share price declined below $5 a share.

A month later, Rahodeb wrote that the Wild Oats’ management “clearly doesn’t know what it is doing . . . OATS has no value and no future.”

Rahodeb even went so far as to defend his own haircut when another user laughed at his picture in the company’s annual report. “I like Mackey’s haircut. I think he looks cute,” wrote Rahodeb, an anagram for his wife, Deborah.

A spokesman acknowledged that Mr Mackey had made postings “under an alias to avoid having his comments associated with the company and to avoid others placing too much emphasis on his remarks”. Whole Foods, owner of the organic Fresh and Wild health food chain, has plans to roll out new Whole Foods outlets across Britain.

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