John Rentoul: It's official (even if it is unfair): Northern Rock has been a huge disaster for the Government

It is not fair, but the Opposition is winning. It is a feeling I first felt when learning about the 1951 election for O-level History. Labour won more votes than the Conservatives but still lost. My feeling was misplaced, I now realise. Labour lost under the rules as they stood – if the rules had been different, people might have voted differently. In any case, a few months later, Labour got its own back, in the February 1974 election, when the Conservatives won more votes but Harold Wilson won four more seats.

I did not notice that aspect at the time, which may have been forgivable in a partisan 15-year-old, but neither did I notice a greater unfairness years later, when Labour gratefully accepted the huge electoral bonus of that business one evening when Norman Lamont swept his hand over his hair and said he was "suspending our membership of the ERM with immediate effect".

Of course, Gordon Brown had been a tenacious supporter of ERM membership, a policy supported by this newspaper and by Gavyn Davies, an economist whose writing I admired. But it did not seem unfair that Labour should benefit from the collapse of the policy. After all, John Major's Government was guilty of other bad things, such as appeasing Serbian aggression in the Balkans, so there was a rough justice to it all.

Now Brown knows what it is like to be on the other side. He and Alistair Darling have acted reasonably throughout the Northern Rock affair. David Cameron and George Osborne, who, had they been in power, would almost certainly have done exactly the same, are guilty of the sheerest cheek in pretending it was all the Government's fault and that it could have been better handled. As Brown said yesterday, there is an air of "student politics" about the Tory leadership. But the Opposition are protected by media consensus, which holds that, as John Humphrys said to Darling on Monday, "You've made a mess of it haven't you"?

The Humphrys-Darling exchange has already become notable for a dispute in the literary criticism branch of journalism over the BBC presenter's use of a quotation from Hansard. Humphrys decided that, because Darling had said, "I agree with my honourable friend", anything his honourable friend had ever said could be used as if Darling himself had said it.

But the interview was worse than that. Before it, Humphrys laid out the facts in accordance with the BBC Charter requirement of impartiality. "We have had months of damaging dithering, delay and indecision," he said. Such an impartial statement of fact that David Cameron was able to say almost the same thing later that day: "The Government is racked by dithering, delay and indecision". Darling said mildly that it was not, but what use is there in patient explanation when the BBC has already – impartially – decided the issue?

Whenever anyone does comment on the specifics of what should be done instead, or, as it usually is, what should have been done, a vagueness descends. It might have been possible to reduce the impact of the collision as the speeding business model hit the wave of the credit crisis if the regulator had acted more forcefully, but does anybody even know the name of the head of the Financial Services Authority? No, but we know Brown set it up and took the supervisory function away from the Bank of England, as if that explains why it didn't work. As for what should be done, "Bank-of-England-led reconstruction," said George Osborne, with the kind of nervousness that would lose a lot of money at poker. "I told you so," said Vince Cable, the Liberal Democrat superhero. But just because he ended up being right does not mean it was wrong to try to find a private buyer.

It doesn't matter, because the damage is done. Everyone knows that Northern Rock has been a disaster for the Government, because Cameron and the BBC say so, even if no one has the slightest idea why. Not that it was obvious why suspending ERM membership was a "humiliation", because as the Eurosceptics pointed out, that was when the economy started to go right. But trying to maintain ERM membership was damaging, as anyone with a mortgage then knew. In the case of Northern Rock no one (except shareholders, for whom public sympathy is limited) has lost money. But it is no use trying to analyse the weaknesses in the Opposition's policy. The trouble for Gordon Brown is that this unfairness is not Northern-Rock-specific.

There are, for example, two other big issues on which Brown hopes Cameron is vulnerable, and on which a large section of the Conservative party can be relied to do everything in its power to assist the Government. One is tax cuts; the other is Europe.

In both cases, Conservative policy is inconsistent. Despite Osborne's iron discipline, he cannot stop himself, his leader and his colleagues implying that they would spend more, tax less and borrow less. Ministers seize on any of these suggestions the moment they are made and say, "black hole". Tory activists likewise, and say, "at last, a bold tax-cutting agenda". Both groups are bound to be disappointed. Cameron and Osborne are not a tortoise and a hare; nor, more importantly, are they idiots. They will stick to Labour's spending plans: that way no hole can open up and swallow them as it did their predecessors.

On Europe, I have also heard suggestions that Cameron and Osborne are divided, with the shadow chancellor favouring a more sceptical policy. I do not believe it. When the Lisbon Treaty is ratified, Cameron will say that it is time to move on, or words to that effect. He won't say it now for obvious reasons, and his position on Europe is confused in all its details. But he will get the big decisions right, on tax and on Europe. Margaret Thatcher, with whom Cameron is currently trying to ingratiate himself after two years of keeping his distance, would understand: There Is No Alternative. No alternative that is remotely likely to give the Tories a chance at the next election, that is.

It is unfair, then, that on these issues, as on Northern Rock, Cameron would not do anything fundamentally different from Brown. Yet Brown is accused of presiding over the disaster of a run on a bank that could have happened at any time and which any government would have tried to sell and then nationalised. He is lambasted for letting public borrowing rise to the same levels that Osborne would plan for. And it is Brown who is assailed for not having a referendum, when the Tories won't have one after the Treaty is ratified either.

Being in Government: it just is not fair.

j.rentoul@independent.co.uk