The 49-year-old Ineos director later denied the claim, reported by the BBC, which came as he announced the Swiss-based company's plans.
The chairman of the Grangemouth branch had been behind a string of warnings that the plant would have to shut within three years unless it could secure a government loan guarantee or achieve wages and pension reforms.
Earlier this month he predicted: "The impact on jobs will be pretty huge. It would also have a big impact on the petrochemicals industry in the UK."
He also pointed out that a typical operator at Grangemouth earned about £55,000 in basic salary plus allowances for shifts, when the average salary in Scotland was £26,000. In addition, he said they had to pay a further £30,000 typically per person for pensions.
Mr MacLean has a university degree in both business and chemistry.
He was a founding member of Ineos, and has played a leading role in acquiring several of the company's assets during his tenure.
He oversees several factories owned by Ineos, with the official title of chairman of Olefins and Polymers Europe.
Mr MacLean claimed the site would be closed by the year 2017 if it continued without investment, and was losing about £100 million a year.