Wednesday's autumn statement will be full of big numbers and arguments about fairness. But Monday's report from Margaret Hodge's public accounts committee on how the biggest companies dodge their fair share of taxes is incendiary, huge in its implications, and ought for once to unite politicians from all sides.

The overall picture is by now familiar to anyone interested in the news: Google, Amazon, Starbucks and many other multinationals are using different jurisdictions and complex accounting rules to avoid paying corporation tax. What the report lays out with new clarity is the terrible imbalance between our national tax-gatherers and the cleverer, sharper corporate accountants, plus the vast scale of the problem – so big it is beginning to feel like a national crisis.

Let's start with scale. The corporation tax take is falling fast, from £46.4bn in 2010-11 to just £40bn in 2011-12. Dwarfing that £6.4bn fall is what Revenue & Customs (HMRC) calls the tax gap. This is the difference between what they think they ought to be collecting and what they're actually collecting. That is an astonishing £32bn.

That's more than the cost of all the state spending on local government. It's not far short of the entire defence budget, and about half of what we spend on education. There's a big, bubbling row about our overseas aid budget. Well, you could fit four of those into the tax gap.

So it's odd, isn't it, that we spend so little time on the subject? When we hear the chancellor on the cost of housing benefit, in-work welfare benefits and child benefit, this week, remember the tax gap. It's a battle that, so far, HMRC is losing. It has apparently been fighting hard to close the gap, but after eight years of trying it has only managed to reduce it by £1bn.

Hodge's committee says HMRC isn't aggressive enough, and is "unconvincingly positive" about the situation. It should not be "so accepting of failure". Reading between the lines, it seems the MPs think Britain's tax-gatherers are simply less bright, less fast moving and equipped with poorer systems than the people they are up against.

This, they believe, will also have a devastating effect at the bottom of the tree, among those dependent on a fast-moving HMRC to fairly allocate and deal with their benefits. Universal credit requires excellent computerised systems, but the department has no contingency planning and its performance on error and fraud has got worse. As a result, "families may find themselves struggling to repay money from much reduced universal credit payments as a consequence of the department's poor performance".

Those people may be looking with increasing awe and anger at what is happening to corporation tax, which Hodge fears is becoming a voluntary tax. But it isn't only them.

When Amazon sells books or games or DVDs at a low price, squirting its profits abroad, it is putting out of business lots of excellent smaller shops that do pay their taxes. The same goes for Starbucks and other coffee shops. We keep being told small and medium-sized businesses are what we're going to rely on for growth. But they are the very ones being hammered by this.

And it goes a lot further than competing businesses. HMRC comes down heavily on the easy targets, the small-timers. But the message that if you are big enough you don't pay your taxes, rots faith in the whole system. In the end, there will never be enough tax inspectors to scrutinise everyone. Taxation depends on assent, and the co-operation, if not the enthusiasm, of those being taxed.

The corporation tax gap destroys it. As the committee says: "There is genuine public anger and frustration because there is an impression that rigorous action is taken against ordinary people and small businesses … But apparently, lenient treatment is given to big corporations …"

So it's not just a battle about the potency of national governments in a globalised marketplace. It's also about the authority of government at home. As this ghastly, endless economic squeeze goes on, it's hard to think of another aspect of domestic policy that is potentially more damaging.

To be fair, George "We're all in this together" Osborne has begun to take note, and the UK is working with other countries to try to find ways to squeeze the biggest global companies out of their tax havens and tax-dodging. And there are the very first signs of a nervous reaction to the bad publicity, with Starbucks – apparently worried by a mass customer boycott – talking to HMRC about paying more tax.

Customer boycotts and consumer activism is all good. UK Uncut has done sterling work in exposing the behaviour of British corporates that don't pay their fair share. With a broken ankle just now, and unable to get out, I'm doing my shopping for Christmas online. It isn't easy to boycott Amazon but I am – and so should we all. (Remember, in the past three years, it paid just £2.3m of corporation tax on more than £7bn of sales here.)

But this can't depend on boycotts. Two things are urgently needed. First, those international agreements to squeeze the multinationals, and that includes zero tolerance for tax havens too. This should become a prime objective of British foreign policy, right now.

Second, HMRC needs a rocket up its hindquarters. It needs better people and tougher leadership, so that it goes after the bad guys in a far more aggressive and determined way. The government can help a lot, by giving it better resources. Here's one area where investment now could pay off dramatically and quickly. We also need to radically simplify the rules. Hodge says that the relevant British paperwork is three feet high, while in Hong Kong it is three inches high.

We're going to see a lot of inter-party fighting this week over tax and spending priorities, in which accusations of unfairness and failing the squeezed middle will be traded in the Commons. But here, surely, is that rare issue that both involves our national interest and should bring MPs together. That makes it sound almost like a war. And, in a quiet way, it is: a war against the globe-trotting corporate cynics that leave mere countries in their wake and have had their way for far too long.

Twitter: @jackieashley