"He should never have been there," the prime minister said of Senator Joyce on the Seven Network's Sunrise program on Friday.
Mr Abbott dumped the maverick Nationals senator from the finance portfolio on Thursday and replaced him with Andrew Robb, a senior Liberal seen by most colleagues as a more appropriate fit for the job.
Senator Joyce, who had held the post since December, becomes the opposition spokesman on regional development, infrastructure and water.
Mr Abbott had shown "bad judgement" in putting up Senator Joyce as the alternative finance minister of Australia, Mr Rudd said.
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"I think it also shows that on these core questions about the economy, big questions arise about
