Leading article: Ex-ministers for hire

Professional lobbying on the US model is a comparatively recent, and regrettable, addition to the rich texture of British political life. This is not to say that it has not existed in one form or other for a long time, rather that the "revolving door" – which allowed MPs and senior civil servants to leave by one exit, only to appear at an adjacent entrance a little later – has become more obvious in recent years, as have the bulging sacks of money on offer. It is also clear, from yesterday's revelations by Channel 4 and The Sunday Times, that efforts made so far to control the practice have been nothing like rigorous enough.

The closeness of the election, of course, makes the accusations against three former ministers particularly damaging, even though they deny any wrongdoing. With the MPs' expenses scandal and the Lords "cash for questions" affair lurking in the background, this also explains why leading members of the Government lined up to express shock and horror. David Miliband, the Foreign Secretary, said he was "appalled", insisting that there was "absolutely no room for anyone to trade on their ministerial office".

Quite so. But the charges are not quite so easily brushed away. Nor is it in any way mitigation that the three Labour MPs in question will be leaving the Commons at the election. All appear thoroughly familiar with the earnings potential afforded by the posts they have held and their continuing access to the corridors of power. We know, not least from the lobbying job the Conservative MP, Andrew MacKay, has landed, that they are unlikely to be the only ones looking to exploit their expertise and contacts in this way.

At present, former ministers must wait one year before lobbying the Government. The Conservative leader, David Cameron, has proposed extending this to two and tightening up the penalties for rule-breaking. We doubt, though, whether even this will be enough. Labour says it will include proposals for a statutory, rather than voluntary, register of lobbyists in its manifesto. The case has now been more than made, and it should not apply only to ministers. Voters are entitled to know whose interests, in addition to those of their constituents, an MP may be representing.