Former vice-president Al Gore said support for corn-based ethanol in the United States was "not a good policy", weeks before tax credits are up for renewal.
He explained his own support for the original program on his presidential ambitions.
"One of the reasons I made that mistake is that I paid particular attention to the farmers in my home state of Tennessee, and I had a certain fondness for the farmers in the state of Iowa because I was about to run for president."
"The size, the percentage of corn particularly, which is now being (used for) first generation ethanol definitely has an impact on food prices.
"The competition with food prices is real."