More rubbish.

A person who files a libel suit isn't put under a full investigation. It's up to the accused libeler to prove the truth of his statement, not for the libeled to open up his life to a full inquiry.  

And that's for 'normal' people. When it comes to politicians, a full investigation is in itself an acknowledgment that you're under a cloud of suspicion. What politician in her right mind would welcome that? Worse yet, as these leaks already prove, information obtained through the investigation is unlikely to remain confidential. Information will be leaked with the intent to damage the person being investigated, even if it points to no wrongdoing.

The original claim, and your defence of it, is wrong. No one in their right mind would welcome a full investigation into their life. At best they would grudgingly tolerate it as the lesser of two evils.