A former Hong Kong reporter of The Wall Street Journal says she'll sue the publication for sacking her because she joined a trade union.

Hong Kong Journalists Association (HKJA) chairperson Selina Cheng has sued her former employer The Wall Street Journal (WSJ), after the newspaper fired her weeks following her election as the leader of the city’s largest press group.

A former Wall Street Journal reporter began proceedings Tuesday to sue the newspaper for "unreasonable dismissal", after she said she was fired for taking up a role heading a Hong Kong press union. "I think the Wall Street Journal has done irreparable damage to my own reputation and the Hong Kong Journalists Association's reputation,