By Reuters Staff (Adds comment from trade union, production minister) BUENOS AIRES, Feb 17 (Reuters) - Argentina is investigating consumer firms including Danone, Procter & Gamble and Unilever, along with food producers like Bunge, over accusations they have deliberately held back production amid a government clampdown on rising prices. The country’s production ministry in a statement alleged that the firms and others had been “holding back production volumes” and had not abided by a resolution to increase output to the “highest degree of their installed capacity.” It said an investigation had found shortages in supermarkets of products ranging from cooking oil to diapers and cheese, and said that the firms under investigation must rectify the situation and restore stock levels.