At the Public Administration Select Committee last week we had Sir Christopher Kelly in front of us. He is chairman of the Committee on Standards in Public Life and, as such, he is one of the many chefs in the kitchen when it comes to MPs’ expenses.

I was quizzing him on the mortgage interest claims of the Leader of the Opposition when the Guardian’s Michael White came in and started scribbling. In his blog on 4 February he wrote that Labour MPs were furious that David Cameron got off lightly.

I wasn’t furious but I do find it difficult to hear Cameron preaching on the issue of MPs expenses when he screwed the system for every last penny of mortgage interest.

Sir Thomas Legg ordered the pay back of excessive cleaning and gardening claims. But retrospection did not apply to mortgage interest – though now the Commons has capped the amount that can be claimed at £1,200 a month.

White wrote: “The Tory leader was smart enough to see that the cleanest way of maxing up the ACA was to slap it all on a mortgage in his Witney constituency (the one with the unruly wisteria) and claim £23,000.”

He went on: “Smart thinking, you may say, as I am inclined to do. Cameron clearly saw it as a legitimate allowance, though it has now been capped at £1,200 per month and will be phased out over five years.”

Well, I don’t think we should applaud Cameron for his smart thinking. The ACA was supposed to cover the additional costs of living in a second home. Electricity and gas, water, council tax. Those sort of things. Not to max out on mortgage interest to finance a large, expensive house, with or without wisteria..

Here is part of my exchange with Sir Christopher Kelly:

Mr Prentice: I said earlier that the Leader of the Opposition claimed £24,000 a year going back five years which went exclusively on mortgage interest, not for a house in the capital but in his Witney constituency. That sounds a bit unfair to me.

Sir Christopher Kelly: This was one of the anomalies.

Mr Prentice: It was a big anomaly.

Sir Christopher Kelly: If the point you make is that one of the anomalies in what happened in the past was that those who claimed only mortgage interest escaped criticism whereas those who claimed for other things within the £24,000 limit did not I agree with you, but you ask whether in that situation it should apply retrospectively. I am pretty clear that the answer to that is no.