Andreas Whittam Smith: Behind the scandals is the shadowy figure of the lobbyist

To exert influence, dupes are needed - which is where the Lords come in

The four members of the House of Lords, who face allegations that they are prepared corruptly to sell their influence on legislation, are minor players in a very big operation, the lobbying industry. Lobbying is not well understood. Its practitioners say they are involved in "public affairs" or "government relations".

Their work is done subtly without necessarily going through transparent channels. And the industry is often underhand. It creates front groups, for instance, and knows how to fake grassroots campaigns and present biased third-party endorsements as if they were independent.

Lobbying cannot exert an influence without a ready supply of dupes – which is where the "Lords Four" come in. Lobbying is done on behalf of a vast array of organisations, from companies to trade associations, from charities to grassroots campaigners. And as this list suggests, there are good and bad reasons for engaging in the activity. The best argument is that much legislation when it first appears is poorly drafted. It is natural that interested parties should seek to get it into a workable form.

Legitimate lobbying, however, wouldn't keep the industry in first-class airfares, chauffeur-driven cars and lunches at the Ritz. Most of the work is done to bring additional business or reduced competition to corporate interests. A recent classic was the remarkable about-face in the Government's policy on the future of nuclear power.

It stated in 2003 that it was "not going to build a new generation of nuclear power stations now". But by 2007 the Government had come round to the view that it would be a "profound mistake" to rule out nuclear power. What had made the difference in such a short time? The economics of power generation hadn't changed a lot nor had knowledge of environmental risks.

Lobbying is the inescapable answer. The Select Committee on Public Administration came as near as it could to saying this when it recently observed: "It is quite extraordinary the number of former MPs and ministers who are now working for the nuclear industry: it includes Geoffrey Norris, Jamie Reed, Jack Cunningham, Ian McCartney, Richard Caborn, Brian Wilson and Alan Donnelly. Some of them also run PR and lobbying firms like Sovereign Strategy which is run by Alan Donnelly and also employs Jack Cunningham."

The Committee also referred to concern that some areas of government policy have effectively been captured at an early stage by interest groups, usually within industry, and that public consultations have been unbalanced in the favour of these interests. The other place to look for large-scale lobbying is the recent decision to create an additional runway at Heathrow airport.

On the campaign maps drawn up for lobbying operations, the House of Lords often features. It does have its advantages even though it is much less important that the Commons. For it plays the role of revising chamber in the legislative process, a function that has grown more significant over recent years. Furthermore, because no party has an overall majority, more horse-trading takes place there than it does in the Commons.

It is also excellent lobbying terrain in other ways. Some 20 per cent of its 700 or so members, for instance, work as consultants for businesses of various descriptions. While there are seemingly strict rules that say that members must publicly state their pecuniary interests at the relevant time, many seem to have "senior moments". Helpful, too, to the lobbying industry is the low calibre of the Lords where a few figures of substance are marooned in a chamber of mediocrities.

There are two methods of dealing with this unsatisfactory situation – the Obama way or the Brown way. The very first measure that President Obama took on entering office was to close what he called the "revolving door" of people who immediately move from government to lobbying. And in stern words that my lords Taylor, Truscott, Moonie and Snape would do well to ponder he said: "Public service is a privilege. It's not about advantaging yourself. It's not about advancing your friends or your corporate clients. It's not about advancing an ideological agenda or the special interests of any organisation. It is about advancing the interests of Americans."

And the Brown way? Declare that it is all very regrettable. Set up an investigation. But close the door as the new US President has done? You must be joking.