Fast food chain Subway is facing criticism over claims that its famous footlong sandwiches are falling short. A man who appears to be from Australia posted a photo on the firm's Facebook page of one of the subs next to a tape measure showing it is in fact 11 inches. Subway is the world's largest fast food chain with 38,000 outlets, and more than 100,000 people have "liked" or commented on the photo, which had the caption: "Subway pls respond." The New York Post carried out its own investigation and found four out of seven footlong sandwiches were less than the vaunted 12 inches. Subway said the length of its sandwiches may vary slightly when its bread, which is baked at each outlet, is not made to the chain's exact specifications. It said in a statement: "We are reinforcing our policies and procedures in an effort to ensure our offerings are always consistent no matter which Subway restaurant you visit." The original photo is no longer visible on Subway's Facebook page, although the company said it did not remove it. But lookalike pictures of the sub surfaced elsewhere on Facebook, and the backlash shows the challenge companies face with the growth of social media sites like Facebook, Twitter and YouTube.