The Philippines’ former top diplomat has waded into the row over the sinking of the FB Gimver 1 in the South China Sea , saying that “China is not to be trusted”. In an outburst likely to dismay Philippine President Rodrigo Duterte , who has been at pains to draw a line under the incident, Albert del Rosario, the former foreign secretary, on Thursday urged Philippine officials to take a tougher stance with Beijing over the sinking – claiming he had “first hand experience” that China’s word was “unreliable”. Del Rosario’s intervention is particularly awkward for Duterte as it comes ahead of this weekend’s Asean summit in Bangkok, which the president is to attend and where the incident is likely to be discussed. Twenty-two Filipino crew members had to be rescued by Vietnamese fishermen when their boat sank near Recto Bank – also known as Reed Bank – last week after a collision with a Chinese vessel . The collision prompted uproar in the Philippines , where protesters on Tuesday burned 22 Chinese flags to symbolise the crew members. But both Duterte and Chinese officials have sought to play the affair down, with the Philippine leader saying it was “ just a collision ”. China, for its part, has vowed to investigate, warning it would be “irresponsible to make political interpretations” out of the sinking. Duterte’s stance has angered some critics who accuse him of being too close to Beijing, with Del Rosario – who has a history of criticising China’s actions in the South China Sea – the latest big name to take aim at his remarks. “When China makes a declaration, you can almost be sure that it is not consistent with what is happening on the ground,” said Del Rosario, who made headlines in March when he asked the International Criminal Court to investigate Chinese President Xi Jinping for “crimes against humanity” over his government’s actions in the disputed sea . Past examples of China’s deceitfulness, according to the former official in the administration of president Benigno “Noynoy” Aquino III, include a promise made during his tenure by a Chinese official not to militarise the South China Sea and an incident in 2012 when Beijing reneged on a US-brokered deal to withdraw ships and end a stand-off with the Philippines Del Rosario was a key figure in the country’s legal challenge against Beijing’s territorial claims in the South China Sea that went before the Permanent Court of Arbitration in The Hague in 2013. The court ruled in the Philippines’ favour, but since coming to power Duterte has taken a less confrontational stance. Away from the political arena, Duterte’s stance on the sinking has won him praise. Action star Robin Padilla, a staunch supporter of the president, said he approved of Duterte’s handling of the incident on the grounds that the Philippines would be no match for China in a war. Meanwhile, Junever Mahilum-West, assistant secretary in the Department of Foreign Affairs, confirmed on Thursday that Duterte would attend the Association of Southeast Asian Nations summit in Bangkok this weekend and said the sinking might be discussed. “There is an opening to raise these issues. Because incidents like [this] emphasise the importance of having a Code of Conduct so that we can avoid and prevent these incidents from happening in the future,” she said.