The Maria Miller affair serves as a cautionary tale to MPs on how not to behave when one's conduct is under scrutiny.

The former Culture Secretary has in one respect been a victim of circumstance: it was not her doing that the Commons Standards Committee rejected the independent parliamentary commissioner for standards' recommendation that she pay back £45,000 in overclaimed expenses. The committee ruled she need only pay back £5800, a decision that has damaged the image of the system of MPs' self-regulation, but that is not Ms Miller's fault.

Nevertheless, she has undermined her own position with her behaviour at almost every turn. She was rebuked by the committee for using delaying tactics and her "legalistic" attitude, and ordered to apologise for it.

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The brevity and tone of her apology to parliament also damaged her. Then of course there was her special adviser's phone call to a journalist on The Daily Telegraph noting that Ms Miller was "having quite a lot of editors' meetings around Leveson at the moment". Even those inclined to be generous, and accept that the words related solely to attempts to prevent intrusion into one of Ms Miller's relatives' lives, can see it was bound to be interpreted as a veiled threat for the paper not to push its investigation into Ms Miller's expenses.

As for claims by the ex-minister's friends that she was the victim of a media witch hunt, that too was misjudged. There is certainly no love lost between the former minister and certain sections of the press, given her responsibility for overhauling regulation of newspapers, but this was no simulated scandal cooked up by journalists. Ms Miller was the architect of her own demise due to her high-handed attitude and the fact she repented only when ordered to do so. MPs have some way to go before winning back public trust following the expenses scandal. Ms Miller's handling of herself during this affair, both as an MP and Cabinet minister, fell short of what the public expect and the press are not only entitled to question her behaviour, but have a duty to do so. It is notable that Michael Gove, deployed yesterday as the mouthpiece of the Cabinet, and Ms Miller have rejected the suggestion of a press vendetta.

Three issues fall out from this affair, the first being the Prime Minister's judgment. Mr Cameron is, on the whole, right not to lop off colleagues' heads every time the press or opposition call for it. Ed Miliband should beware; all party leaders are eventually faced with the unenviable choice between standing by a colleague and cutting them adrift. Now that the Labour leader has made such capital out of Mr Cameron's discomfort he can expect no mercy when his time inevitably comes. Even so, Ms Miller's handling of this issue was problematic from the start. The Prime Minister has a duty, not just to his colleagues, but to ensure that standards are seen to be upheld, a far more significant matter since the fragile reputation of parliament depends upon it. Mr Cameron appeared rather slow to accept this.

The second issue is that there are now just five women attending Cabinet, out of 34. Eighteen ministers are privately educated, with 24 having attended Oxford or Cambridge. This Government is now as it has always been: sadly unrepresentative of the country it serves.

Perhaps the most serious consequence of this affair, however, is the way it has exposed the shortcomings of the system to uphold MPs' standards. The rules on MPs' expenses have been significantly tightened, but parliamentarians may still disregard the advice of the standards commissioner when it comes to one of their own, as happened here, though the committee argues that new information came to light from Ms Miller after the standards commissioner finished her investigation, and this informed their final decision. The 10 MP members of the standards committee have a vote; its three lay members do not. The best way to build public confidence would be to ensure MPs were no longer responsible for sanctioning themselves. Instead, an external disinterested body should have that duty, earning it the respect of all MPs.