Contractual workers

We are looking into the case of contractual workers working with PAGIBIG. We want to know whether it is legal to keep them working as contractuals - some of them for a period of thirteen years and over. From the information that we gathered, these workers are recruited by DBP and then are assigned to PAGIBIG. DBP gets 40% of the monthly salaries of the workers as its fee. PAGIBIG reviews the case of the workers every after six months and use that as a basis on whether or not to renew their contract. This is to us a very exploitative arrangement. We would like to take on the cause of these workers and are currently exploring possible actions to take. We would like to know what you can advice. Thank you so much