The embarrassment that has shaken British politics since its MPs' expense claims were brought to light, has prompted two members of the New Zealand Parliament, both candidates in the Mt Albert byelection, to publish their reimbursements. Now their parties, and others, are talking of following suit.

This must be awkward for Speaker Lockwood Smith who refused to release Parliament's record of expenses in the wake of the British scandal. "Individual members are under enough scrutiny as it is," he said.

Dr Smith was equally protective of privacy in the halls of power when it emerged recently that a number of professional lobbyists have privileged access to Parliament Buildings. He issues them with door passes if they say they need to visit at least three times a week and an MP endorses their request. But to name them, he said, would breach their business privacy.

His concern was somewhat undermined by two of them who promptly identified themselves, one explaining that their passes did not extend to minister's offices and were of limited value really.

Really? The subject of MPs' expense claims might be more salacious, but the activities of lobbyists are of much more significant public interest. Lobbyists make it their business to keep as close as they can to officials and political staff in areas of public policy of possible interest to their clients. They can be more effective if they hear about proposals early, before powerful people take public positions that can be hard to budge, or before opposing interests can get organised.

Legislation and regulations can be considered and defeated by lobbyists before the public knows anything is afoot.

Lobbying is an inevitable adjunct to politics everywhere and it maintains a flow of information between public decision-makers and industries directly affected by their decisions. Acts of government are probably improved by the exchange more often than not.

But sectoral interests and the public interest are often in conflict and the task of upholding the public interest in dealings with lobbyists should not be left entirely to the public officials and politicians in the room. Public disclosure would help.

The Green Party has called for a public register of those who enjoy privileged access to Parliament, with a list of their clients. That would do no harm. With knowledge of who they represent it should be possible to monitor their influence more closely.

One of President Obama's first acts on taking office was to order new rules for White House lobbyists, or "special interests" as he had called them in his election campaign. A public register of lobbyists has long existed in the United States, as well as in countries such as Canada and Australia. Mr Obama's new rules go further, such as preventing former public servants setting themselves up as lobbyists for firms dealing with their old departments.

There is no need to go that far. If Government staff want to retire and trade on their inside knowledge of the power structure, and contacts within it, there seems no reason they should not - so long as we know they are doing so, and we know who is hiring them.

The Speaker has dismissed the Greens' call too lightly. There can be no legitimate privacy about the business of bending the Government's ear. If lobbyists have a case to make for or against a matter of public policy their work should stand public scrutiny. It commonly occurs before policy proposals reach the stage of open public submissions. The public ought to know more about these discussions and a register of lobbyists and clients would help let some light in.