A UK academic has resigned from the steering committee of the Food Standards Agency's public dialogue on the use of genetic modification.
Professor Brian Wynne from Lancaster University, who was vice-chairman of the group, raised doubts about its impartiality.
In a resignation letter, he said he was concerned that the agency operated from a pro-GM policy stance.
But the FSA said it was committed to a balanced public dialogue on the issue.
Professor Wynne's resignation from the committee comes just a week after that of Dr Helen Wallace, director of UK public interest group GeneWatch.
She said the committee's dialogue was "an integral part of the GM industry's public relations strategy".
In his letter Professor Wynne took issue with specific comments made by FSA chair Jeff Rooker at a recent meeting of the steering committee.
He quoted Mr Rooker as saying that the public was "anti-science" and that GM was a "scientific issue".
Since "FSA policy is determined only by sound science", Professor Wynne said that this position implied that a "pro-GM policy stance was implicit in the FSA's "deep institutional culture".
He had concluded, he said, that "the integrity of the very policy process" had been compromised.
Professor Wynne told BBC News that the FSA was unaware that "its own premises... leads it to a pro-GM policy while saying with a straight face that it is impartial on the issue".
"I am not prepared by default to aid and abet this kind of systematic failure of institutional integrity in what is a crucial public arena," he added.
The FSA responded: "We take no stance on GM apart from the pro-science one."