I've just been talking to Simon Evans from Thames Water, who told me the company has a "clear conscience" - despite our biggest water company paying no corporation tax for the last three years.
So how can he defend that? Especially as the water regulator, Ofwat, suggests the behaviour of some of the water firms is "morally questionable?"
Well, Evans is robust on the question, saying they are doing exactly what the government wants - spending hundreds of millions of pounds on new infrastructure that can perfectly legally be written off against tax.
And carrying very high levels of debt, the interest on which can be, perfectly legally, written off against the tax bill.
But perhaps the question of tax has, fairly or unfairly, gone beyond what is legal and what is not.
That may not be right, or indeed fair, but increasing numbers of politicians and now the regulator are questioning what is moral too.
Last year, the coffee company Starbucks found that public pressure over fairness and morality, not the law, was enough to make them offer to pay tax they didn't owe.
Later this week the Westminster committee that has done a lot to raise this issue, will publish its report into the tax affairs of Google, who Margaret Hodge, its powerful chairman accused of doing "evil" by paying only small amounts of corporation tax.