London, May 12 : Organic farming, one of Prince Charles' greatest passions, has been challenged by none other than his own father Prince Philip, the Duke of Edinburgh.
During a television interview for ITV1 fly-on-the-wall documentary, The Duke: A Portrait of Prince Philip, the royal took Sir Trevor McDonald on a tour of the Sandringham estate and questioned the benefits of organic farming.
"Organic farming is not an absolute certainty that it's quite as useful as it sounds," the Telegraph quotes Prince Philip, as saying in the documentary.
"You have got to be emotionally committed to it - but if you stand back and be open minded about it, it is quite difficult to really find where it has been a real benefit," he adds.
The Duke's remarks will be seen as a challenge Prince Charles, who is a staunch supporter of organic farming.
The Prince of Wales first started using the organic system two decades ago at his country estate Highgrove.
Though he was first ridiculed for the venture, it has proved to be quite a success.
"It's interesting now that it isn't ridiculed to the same degree. I think people are beginning to realise that some of the chickens are coming home to roost and settle heavily in the genetically modified trees," Charles has said.
The two-part documentary is to be screened on May 12 on ITV1 in the UK and concludes at the same time on May 13.