David Cameron's tax affairs are a gift to Jeremy Corbyn. His survival depends on what he does next

Whatever else people think of Corbyn, they know he is unlikely to have benefited from an offshore trust fund

Labour leader Jeremy Corbyn can tap into the public's anger over how wealthy elites conduct their tax affairs (Getty)

The tax row engulfing David Cameron is a golden opportunity for Jeremy Corbyn. On the BBC’s Andrew Marr Show this morning, the Labour leader suggested that he can exploit it. He insisted that it was not about “class war” but openness.

Calmly, he articulated the anger of ordinary people – the care workers, cleaners and nurses who are fined if they don’t pay their taxes, and cannot negotiate how much they pay with HMRC like the rich. Such a measured approach, if maintained, will strike a chord with middle-class voters too.

Mainstream parties across Europe are losing votes to anti-establishment parties on both left and right, as they capitalise on the anger of ordinary people struggling since the financial crisis while they see the rich still get richer. But could Labour under Corbyn buck that trend?

Corbyn and John McDonnell, the shadow Chancellor, campaigned for “tax justice” years before it became flavour of the month. Voters know Corbyn is a million miles from New Labour, which might work to his advantage while politicians’ finances remain in the headlines.

Whatever else people think of Corbyn, they know he is unlikely to have benefited from an offshore trust fund. His tax return, when he sorts out his paperwork, is likely to be boring indeed.

Cameron allies hope that, in the absence of damaging revelations in the tax returns summary he has published, the public will judge that they have not learnt much new. They insist his rich background was “factored into the price” when voters made Cameron prime minister last year. His allies argue that voters think that politicians of every hue are in it for themselves. And so, when the dust settles, they hope that nothing much will have changed.

But the dust may not settle quickly. Other Conservative ministers, and possibly all MPs, will surely now have to disclose their tax returns for past six years too. There are bound to be further revelations, and they could easily blow apart Cameron’s hopes of ending the Tories' image as the “party of the rich”.

Voters might view Corbyn as not like most politicians – after all, he is not. The authenticity that shined through during the Labour leadership contest could now reach the parts of the electorate he has not yet reached.

The timing of the Panama Papers leak could be the first real bit of luck for Corbyn in his six months as Labour leader. His early months were dominated by foreign and security issues on which he was at odds with a majority of his MPs.

There is no reason for Labour to argue with itself about tax avoidance. However, Corbyn will have to ensure that his enthusiastic supporters are not tempted to wage class war, which might repel many of the voters Labour could win over in these new times.

If Labour plays it right, the party could do better, and the Conservatives worse, than expected in next month’s elections for London Mayor, local authorities, the Scottish Parliament and Welsh Assembly.

Paradoxically, that would not please many Labour MPs. A strong Labour performance would make it harder for Corbyn’s critics in parliament to go ahead with their plans to oust him this summer. To head off an attempted coup, he may also need to up his game at Prime Minister’s Questions and land some serious blows on Cameron. That could tip some wavering Labour MPs against joining a revolt against him this year.

But he will have to be forensic and effective. If he missed the open goal, as he did after Iain Duncan Smith’s resignation, it would play into the hands of his critics, reinforcing their message to party members that their leader is simply not up to the job.

For Corbyn, as well as Cameron, the stakes in the great tax controversy are very high.