(1) Where the immediate employer of any worker is himself in the employment of some other person and the worker is employed on the premises of that other person, that other person shall for the purposes of this Part be deemed to be the employer of the worker jointly with the immediate employer.

(2) Where an employer is charged with an offence under any section or subsection contained in this Part, he shall be entitled, upon information duly laid by him and on giving to the prosecution not less than three days' notice of his intention, to have any other person to whose act or default he alleges that the offence was due brought before the court hearing the charge at the time appointed for the hearing of the charge, and thereupon the following provisions shall have effect -

(a) if, after the commission of the offence has been proved, the employer proves that the offence was due to the act or the default of that other person, that other person may be convicted of the offence,

(b) if the employer further proves that he has used all due diligence to secure that this Part and any relevant regulation or order made thereunder were complied with, he shall be acquitted of the offence.

(3) Where a defendant seeks to avail himself of subsection (2) of this section -