UK Member of Parliament Patrick Mercer has resigned under accusations that he took cash (from journalists pretending to be lobbyists) to ask questions in the House of Commons. It has renewed calls for lobbyists to be registered and regulated in order that we know who our MPs are talking to.

Regulations invariably have the opposite effect of those intended. Such a move would damage independent debate. After all, policy think-tanks also talk to MPs. They may be utterly independent, getting their funding from public subscriptions rather than from companies. But if any organisation that talks to an MP has to register itself as a 'lobbyist', what is the result.

We have seen the result in the United States. Think-tanks carry on as before, but they have to set up a separate 'lobbyist' body comprising any of their personnel who have frequent discussions with folk on Capitol Hill. The effect is to politicise think-tanks and put a wall between their independent policy experts and the politicians. An issue comes up, a think-tank expert has important things to say, but cannot say them directly to the policymakers.

What is the best solution? Doctor, heal thyself. MPs should certainly declare their interests and whom they take favours from. But if MPs could be subjected to recall motions by their constituents, they would be a lot more careful about taking favours from business – and perhaps more careful to listen to independent policy advice.

Ultimately, though, if individuals ran their own lives and Parliament had a lot less power, it wouldn't be worth lobbyists (and journalists, let's remember)  trying to bribe them.