If this has been a bad week for the Conservatives, it has been even worse for politics as a whole. The Derek Conway affair, so hot on the heels of the various controversies about donations to the Labour Party and to the campaigns of individual Labour politicians running for office, inevitably generates loose talk about "snouts in the trough". Mr Conway's misdemeanour is a more clear-cut political scandal, not only because it involves looting the public purse, but also because his family benefited personally from his largesse with our money. Inevitably, it has given rise to calls for a ban on MPs employing family members, as is the case in the US.

If this has been a bad week for the Conservatives, it has been even worse for politics as a whole. The Derek Conway affair, so hot on the heels of the various controversies about donations to the Labour Party and to the campaigns of individual Labour politicians running for office, inevitably generates loose talk about "snouts in the trough". Mr Conway's misdemeanour is a more clear-cut political scandal, not only because it involves looting the public purse, but also because his family benefited personally from his largesse with our money. Inevitably, it has given rise to calls for a ban on MPs employing family members, as is the case in the US.

At present, the practice is widespread at both Westminster and Holyrood. (In 1999 civil servants advised MSPs in draft guidance to ban the practice but the idea was rejected.) There are valid reasons for allowing the continuation of the practice of legislators employing their spouses (usually wives as secretaries). Across the political spectrum, there are examples on the payroll of hard-working wives who represent excellent value to the taxpayer in a profession that otherwise can place great strain on domestic relationships through enforced separation. Indeed, it would be fundamentally inequitable to exclude one group of people from particular jobs on the basis of marital ties. The case for employing one's grown-up children as researchers is less clear-cut for several reasons. It is more difficult to log their work and, because a researcher's post is often the coveted first rung on the political ladder, such appointments are vulnerable to the charge of nepotism. Such was the scale of Mr Conway's misuse of public funds in "employing" his two sons that the status quo is now untenable. The case merely deepens public cynicism about politicians in general. An arrangement that has relied on self-regulation and "honourable members" has been shown to be unfit for purpose. At Westminster, John Lyon, the newly-appointed parliamentary standards commissioner, must now look at how expenses and allowances can better be scrutinised. And the current review of allowances at Holyrood must include the issue of employing family members.

The call from some quarters for legislators' support staff to be employed directly by parliament, as in the European Union, may create as many problems as it solves and would not necessarily bring more clarity to what they do for their wages. And while there are calls on all sides for more transparency, the public's right to know has to be balanced against the individual's right to privacy under the Data Protection Act. Reform may be necessary, but much will turn on the precise mechanism adopted to deliver it. At the least, members of both parliaments (and the Welsh Assembly) should be required to keep timesheets that would be subject to spot checks by an independent body, such as the National Audit Office and Audit Scotland. Events this week have shown that the current arrangements are open to abuse. Legislators require proper support for their staff but such expenditure must be properly accounted for.