Governor-General Quentin Bryce on Tuesday congratulated Senator Carr on his appointment, which was announced by Prime Minister Julia Gillard earlier this month.
"Congratulations to you," she told Senator Carr, after inviting him to take the oath in front of a small crowd including his wife Helena and Ms Gillard.
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Senator Carr replaces Kevin Rudd who left the post after an unsuccessful challenge against Ms Gillard for the Labor leadership.
Earlier, Carr appeared in Parliament to begin the formal processing of being sworn in as a federal senator, after pledging continued Australian support for the war in Afghanistan as well as launching a stinging attack on 'cheapskate hypnotist' Tony Abbott.
