Where any person claiming to be the owner of copyright in any work, by circulars, advertisements or otherwise, threatens any other person with any legal proceedings or liability in respect of an alleged infringement of the copyright any person aggrieved thereby may, notwithstanding anything contained 1[in section 34 of the Specific Relief Act, 1963 (47 of 1963)], institute a declaratory suit that the alleged infringement to which the threats related was not in fact an infringement of any legal rights of the person making such threats and may in any such suit--

(a) obtain an injunction against the continuance of such threats; and

(b) recover such damages, if any, as he has sustained by reason of such threats:

Provided that this section does not apply if the person making such threats, with due diligence, commences and prosecutes an action for infringement of the copyright claimed by him.