David Cameron was right to withdraw the Conservative whip from Derek Conway, although he should have done so earlier. For a Member of Parliament to employ a teenager as a parliamentary research assistant is decidedly odd. For an MP to pay his own son £43,000 in salary and bonuses, while that son was a full-time student at the University of Newcastle, is simply staggering. That's nice work if you can get it. No other undergraduate could ever have got it, and Conway junior should never have got it. While this may have been an ingenious response to the introduction of university tuition fees, it was also a blatant misuse of public funds.

The brazen nature of Mr Conway's actions is breathtaking. The Standards and Privileges Committee could find “no record” of any actual work that Conway junior had done. He was, according to the Parliamentary Commissioner for Standards, “all but invisible during the period of his employment”. Mr Conway had insisted that his son was providing valuable briefings on foreign affairs. It is hard to know why a backbench MP would turn to a Newcastle university geography student for up-to-the-minute international insights, rather than the House of Commons library. The only part of this story that could be called exotic is the suggestion that the research post has in fact been gifted not once, but twice: handed down from an elder to a younger son.

The case has rattled many MPs because the practice of employing family members at taxpayers' expense is widespread. It is also perfectly legal. That makes it even more vital to distinguish between employment that is proper and employment that is not. Some relatives are well qualified, take the job seriously and produce excellent value for money, precisely because of their personal commitment to the MP. It would be a shame to exclude such people from the system altogether. The application process for jobs must, nevertheless, be open and transparent, and relatives must be able to show that they are qualified, rather than just related.

MPs have an allowance of £80,000 to employ staff, who must be issued with proper contracts and “employed to meet a genuine need”. The onus should be on those staff to demonstrate that they are up to the job and performing well. Any who are not should be rethinking their positions rapidly after the humiliation of Mr Conway, whose parliamentary career has effectively been ended by the removal of the whip.

There has been too much public outrage about “fat cat” MPs. Criticism of parliamentary pay is misplaced. The fact is that our politicians are woefully underpaid. It is wrong that those who lament the poor calibre of some MPs simultaneously insist that they deny themselves even the most humble salary increase. The public rightly demand the highest standards from those who seek public office. If we want a professional political class, we must pay professional rates. Politics is an honourable endeavour, as is donating to political parties. Abuses must be ruthlessly rooted out. Yet there should also be no need for MPs to feel so badly underpaid that they grub around for funds in grubby places.

The only positive aspect of this sorry tale is that the system has found Mr Conway out. The message should be clear: you cannot keep it in the family and get away with it.