In this cynical, media age, it is not easy for an organisation to establish a strong reputation for taking complicated facts and delivering sound and sober judgements upon them, but you’d have to say the Institute for Fiscal Studies has done so.

There were times when I was working for the government when their judgements could be a pain in the neck, and their sanctimoniousness could be a bit off-putting at times too. But the reason for the pain was the knowledge that they were taken seriously inside and outside the Westminster-Whitehall bubble, and they were often right.

That is why both the Tories and the Lib Dems, when in Opposition, would leap on any criticism the IFS made of Gordon Brown’s economic approach.

So as Nick Clegg rages at the IFS over their factual observation that the Spending Review was regressive, ie hitting the poorest hardest aka unfair, let us add the IFS to the list of things on which the DPM has stood on his head since May 6.

Both Clegg and David Cameron looked a bit uncomfortable taking questions from the public yesterday. The beginnings of real anger at the unfairness of some of their decisions was coming through. That anger will grow when the decisions are implemented. And I was not at all surprised to see Clegg popping up in The Guardian trying to assure Lib Dems that values of fairness underpinned the approach to the CSR.

But the paper’s front page, even without his help, rather torpedoed that. The IFS report on the regressive nature of the overall package; and their other main story about the bankers breathing a big sigh of relief that the planned levy is not going to hit them very hard at all.

And over on the letters page, someone pointing out that the extra welfare cuts on top of those announced in the budget – £7bn – is the same sum enjoyed by bankers in bonuses. Fair? Don’t think so, Nick. Or ask yourself this … if the Tories had got a majority, and you had still been in Opposition, would you have said it was fair? No, didn’t think so.

There is also a lot more unravelling to do on the pupil premium. A perfecfly fair idea in many ways. More for those at the bottom end .. like it. But the money is coming from the schools budget which they all claimed was being protected. It isn’t. It means spending per pupil for the average will fall, n’est-ce pas Nick. Fair? No.

What the IFS has shown is that on big arguments, it is possible to push this lot back fairly quickly. Even with most of the media still in bottom-kissing mode, I reckon before too long it will be well established with public opinion that this package is not fair.

Meanwhile Labour needs to push back hard, strategically and over time, on the ‘it’s all Labour’s fault’ part of the Tory argument. It can be done. And it needs to be done, with the same doggedness and attention to detail that has got the IFS established as such a strong voice in this area.