Patents Act, 1970
(1) Where the Controller is satisfied, upon consideration of an application under section 84, section 86 or section 89 that a prima facie case has been made out for the making of an order, he shall direct the applicant to serve copies of the application upon the patentee and any other person appearing from the register to be interested in the patent in respect of which the application is made, and shall advertise the application in the Official Gazette.
(2) The patentee or any other person desiring to oppose the application may, within such time as may by prescribed or within such further time as the Controller may on application (made either before or after the expiration of the prescribed time) allow, give to the Controller notice of opposition.
(3) Any such notice of opposition shall contain a statement setting out the grounds on which the application is opposed.
(4) Where any such notice of opposition is duly given, the Controller shall notify the applicant, and shall give to the applicant and the opponent an opportunity to be heard before deciding the case.