Section 12A. If any producer is paid by a milk dealer less than the minimum price for the sale or delivery of milk, as fixed by official order or orders of the commissioner, such producer may recover in a civil action against such milk dealer the full amount that would have been due him for such milk at the minimum price as so fixed, less the amount actually paid him for said milk, together with costs and such reasonable attorney’s fees as may be allowed by the court, and any agreement between such producer and such milk dealer to sell or deliver milk for less than such minimum price shall be no defence to such action. At the written request of any such producer paid less than the minimum price for such sale or delivery of milk to which such producer is entitled under the provisions of the official order or orders of the commissioner, the commissioner may take an assignment of such claim in trust for the assigning producer and may bring an action to collect such claim, and such milk dealer shall be required to pay the costs and such reasonable attorney’s fees as may be allowed by the court. The commissioner shall not be required to pay any entry fee in connection with any such court action.