Of the 20 countries with a high prevalence of child marriages, 12 are in the Commonwealth -- including India.
None of the Commonwealth's democratic or development goals can be achieved without first empowering its girls and women, who represent more than half of the Commonwealth's two billion people, a statement said.
The statement was issued jointly by the Queen, Quentin Bryce, Governor General of the Commonwealth of Australia, Surujrattan Rambachan, Foreign Minister of Trinidad and Tobago and Malcom Fraser, former Prime Minister of Australia.
Early and forced marriage is one of the most significant barriers to girls' education, maternal health, female economic empowerment and the realisation of basic, fundamental human rights, it added.
In her address at the inaugural, Commonwealth head Queen Elizabeth II had said: "The Commonwealth theme this year is 'Women As Agents of Change'. It reminds us of the potential in our societies that is yet to be fully unlocked, and it encourages us to find ways to allow all girls and women to play their full part.
"We must continue to strive in our own countries and across the Commonwealth together to promote that theme in a lasting way beyond this year."
The Commonwealth has a strong foundation of commitments, conventions and treaties on which to act towards gender equality, like its Plan of Action for Gender Equality 2005-2015.