If a member of a trade union which has a political fund certifies in writing to his employer that, or to the effect that —
the employer shall ensure that no amount representing a contribution to the political fund is deducted by him from emoluments payable to the member.
The employer's duty under subsection (1) applies from the first day, following the giving of the certificate, on which it is reasonably practicable for him to comply with that subsection, until the certificate is withdrawn.
An employer may not refuse to deduct any union dues from emoluments payable to a person who has given a certificate under this section if he continues to deduct union dues from emoluments payable to other members of the union, unless his refusal is not attributable to the giving of the certificate or otherwise connected with the duty imposed by subsection (1).