The British citizen must give public notice for one week (7 days) in his/her local newspaper (in Australia). In cases where both partners are British citizens, each person must make a separate notice.
It is essential that the newspaper notice(s) be worded as follows:
“I, [full name], bachelor/widower/divorcé, of [full address] intend to marry [full name of fiancée], spinster/widow/divorcée, of [full address] at [name and address of place where marriage is to be solemnised] on [date of marriage]. Any person knowing of any lawful impediment to the marriage should notify without delay the Consular Section, British High Commission, Locked Bag 5011, Passport Section, Piccadilly House, 39 Brindabella Circuit, Canberra Airport ACT 2609.
The British citizen should send all seven pages of the relevant newspaper (the whole page containing the same notice published on seven consecutive days in the same newspaper) along with the following documents:
a photocopy of the applicant’s full birth certificate
a photocopy of their British passport
a photocopy of the divorce decree for every marriage (if the applicant has been married previously)
an original affidavit
NB: All applicants must swear an affidavit to the effect that the applicant is free to marry, in front of a Notary Public (not a Justice of the Peace) in Australia before they leave for overseas to get married. Where both partners are British citizens, each person must swear an affidavit.
If no objection to the marriage is received within twenty-one (21) clear days, the Consular Officer in Canberra will inform the Consular Officer in the consular district where the marriage is to take place. The Consular Office in that country is then responsible for issuing the CNI.
Please see following website for further details and regulations - http://ukinaustralia.fco.gov.uk/en/help-for-british-nationals/living-in-australia/notice-intend-marriage