TOKYO—Farallon Capital Management on Tuesday urged Toshiba Corp to secure the legally required support of two-thirds of its shareholders before the Japanese industrial conglomerate continues with a controversial plan to split in three. U.S. hedge fund Farallon, Toshiba’s third-largest shareholder with a stake of more than 6 percent, joined the second-largest investor 3D Investment Partners in demanding a higher threshold for the break-up plan. Since Toshiba is nearly 30 percent owned by foreign funds, many of which appear to oppose the split, setting the 67 percent bar could force the conglomerate to ditch its plan. Toshiba should seek approval from two-thirds of its shareholders “before it risks expending significant time, cost, and management resources on the separation plan,” Farallon said in a statement. “The separation plan without shareholder trust would achieve nothing but the creation of three discrete companies, with each inheriting the same issues as Toshiba,” it said. Toshiba …