A US court has refused to revisit its ruling that a district court should have granted the Federal Trade Commission an injunction to block Whole Foods Market's acquisition of smaller rival Wild Oats.

A panel of three judges from the US Circuit Court of Appeals for the District of Columbia found in July that the merger should have been blocked.

"The district court committed legal error in assuming market definition must depend on marginal consumers; consequently, it underestimated the FTC's likelihood of success on the merits," the court found.

The ruling revived the FTC's attempt to block the merger of the natural and organic food retailers.

Whole Foods responded by calling for an "en banc" hearing, that would have involved all of the appeals court's judges. However, the appeals court rebuffed this move on Friday (21 November), stating that its earlier ruling still stands.

Whole Foods completed its US$565m takeover of Wild Oats in August last year. However, the FTC has continued to question the validity of the merger, arguing that the deal breaks competition laws.

The FTC is set to hold full administrative hearings into the deal in February.