The local authority and the Board shall not be liable in damages for any irregularity committed by their officers in the execution of this Act, or for anything done by themselves in the bona fide execution of this Act; and every officer acting in the bona fide execution of this Act shall be indemnified by the local authority under which he acts in respect of all costs, liabilities, and charges to which he may be subjected ; and every action or prosecution against any person acting under this Act on account of any wrong done in or by any action, proceeding, or operation under this Act shall be commenced within two months after the cause of action shall have arisen; provided that nothing in this section shall exempt any member of any local authority from being surcharged with the amount of any payment which may be disallowed by the auditor in the accounts of such authority, and which such member authorised or joined in authorising.