A certificate of registration of a Trade Union may be withdrawn or cancelled by the Registrar--

   (a)  on the application of the Trade Union to be verified in such manner as may be prescribed, or

   (b)  if the Registrar is satisfied that the certificate has been obtained by fraud or mistake, or that the Trade Union has ceased to exist or has wilfully and after notice from the Registrar contravened any provision of this Act or allowed any rule to continue in force which is inconsistent with any such provision, or has rescinded any rule providing for any matter provision for which is required by section 6:

   ¹[(c)  if the Registrar is satisfied that a registered Trade Union of workmen ceases to have the requisite number of members:]

   Provided that not less than two months' previous notice in writing specifying the ground on which it is proposed to withdraw or cancel the certificate shall be given by the Registrar to the Trade Union before the certificate is withdrawn or cancelled otherwise than on the application of the Trade Union.