Leading article: We must preserve what is best of the House of Lords

The case of four members of the House of Lords who apparently offered to influence legislation in return for a fee has been greeted by general uproar. It is not surprising, given the echoes of the toxic "cash-for-questions" affair that convulsed the House of Commons in the 1990s.

This latest scandal emphasises the lack of transparency in relation to the lobbying links of peers and also the vagueness of the rules governing their behaviour. Whatever the results of the inquiry into the conduct of the four peers, the system manifestly needs to be tightened up.

The argument that this is merely a case of a few bad apples will not do. There have been several recorded instances of peers handing their Westminster passes, intended for researchers, to lobbyists. And how many of us were aware before this week that 145 of the 743 members of the Lords are engaged in paid consultancy work? Most of these peers are doubtless offering innocent political advice for their services, rather than altering legislation in their clients' interests. But the point is that the present disclosure arrangements leave a good deal of room for doubt. At the very least, peers should be compelled to reveal how much they are earning from their outside interests.

Such problems flow from the half-reformed nature of the House of Lords. The Government cleared out most of the hereditary peers in 1999 but, in other respects, the House remains as unaccountable as it ever was. Nowadays, a peer is appointed rather than born to the title, but the seat is still considered his or her personal property. They cannot be expelled from the house or stripped of their titles for corruption; not even if they end up spending time in prison for their crimes. It is difficult for a democracy to tolerate an upper chamber that is, in many respects, a feudal relic.

All this is true. And yet some wider perspective is important in considering the future of the second chamber. It is important to remember that many peers do much good work painstakingly picking through the legislation that is sent up by their professional colleagues in the Commons. When they come across something wrong-headed or dangerous, they send it back. And most of them perform this service for no salary. The lords have certainly proved their worth as a revising chamber in recent years. Last year, the House rejected the Government's legislative plans to detain domestic terrorist suspects for 42 days without charge. In 2005, the law lords ruled that the Government's internment of foreign terror suspects was incompatible with the European Convention on Human Rights.

The argument for completing the reforms set in train a decade ago is strong. At least a proportion of peers should be made democratically accountable to the electorate, but a wholly elected chamber would be a mistake. The last thing we want is another chamber of professional politicians. It is worth asking whether the House of Lords would have proved such a stubborn check on the Commons over the years if it had been full of individuals keen to secure party funds for re-election? It is unfashionable to speak of non-partisan public service in the present cynical era, but there is still a place for it.

By all means, let the Government clean up and reform the Lords, but in the process we need to be careful not to wipe out what makes the chamber such a valuable check and balance on our democracy.