After years when ministers were far too reluctant to resign, clinging on to their jobs regardless of criticism, the case of David Laws has rather turned that on its head.

I say that because, for me, the dividing line between reprimand and resignation in matters of personal financial affairs should be whether or not you have personally gained from a breach of the rules. Even if it turns out David Laws broke the rules (and the Parliamentary Commissioner is yet to rule on quite how "partner" should be defined), he has claimed far less in expenses than he could have had he decided to go public with his personal life several years ago. So, in this ironic situation where a politician gets into trouble for claiming less money than he could have done, I regret that he has decided to resign.

Of course, some have said that Laws should have been more careful to keep on the right side of the rules. However, the coverage by The Telegraph of Danny Alexander's tax affairs – and the subsequent reaction of some of the public – shows that even that is not enough to avoid criticism.

In Danny Alexander's case the capital gains tax rules are clear: he did not switch around any definitions to exploit them and he followed the same rules that apply to the rest of us. Yet sill The Telegraph criticised.

It's an odd form of morality to criticise someone for paying no tax when there's no tax to pay. It's like criticising someone for exploiting loopholes by putting money into a pension. You get a tax break if you do that, but it's not dodging tax – it's just how the system is designed to work.

The oddity of The Telegraph's standards is heightened if you read the advice it gave its own readers in June 2007. That piece gave 10 tips on how to avoid paying capital gains tax and approvingly quoted a tax consultant saying, "It is possible to reduce a tax bill of a few hundred thousand pounds to virtually zero". Imagine if an MP had been caught distributing such a list.

There are two dangers than come with this inconsistent "you're a politician so what you've done must be wrong even if it's better than how I behave" mindset. One is that it makes politicians blank out the media and claim what they can anyway – because if you're going to be criticised regardless, why bother listening to the critics?

The second is that it puts good people off politics. Why put yourself and your family up for such treatment when there are so many other fulfilling careers? There was no need for The Telegraph to run a snatched doorstep photo of David Laws's partner – but it is standard fare for political coverage across the media.

How many talented people will have looked at the story thinking, "Why risk putting my partner through that?" In the end, we all lose if such people are put off – because the complexities and opportunities of government are so great that we need the very best in Parliament.

Mark Pack is head of innovations for the Liberal Democrats