Pietersen was axed from all England duty on Tuesday, with officials at the England and Wales Cricket Board (ECB) citing a need "to rebuild not only the team but also the team ethic and philosophy" following the side's 5-0 Ashes thrashing in Australia.
But the departure of the gifted Pietersen, and in particular the ECB's lack of clarity over why he was being jettisoned, has provoked a huge public backlash.
Morgan was previously editor of Britain's Daily Mirror tabloid newspaper, a traditional supporter of the main opposition Labour Party and a staunch critic of Cameron's Conservative-led coalition government.
But Cameron, in an interview broadcast today by BBC Radio Lancashire, said he found himself in "sympathy" with Morgan regarding Pietersen.
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"I am an enormous fan of Kevin Pietersen and I have had some of my most enjoyable times watching him tonking the ball all over the park," Cameron said.
"But I will let the England selectors pick the England team, I think I had better stay out of this one.