As Labour gathers in Manchester it is clear to all that things have to change if Gordon Brown is to have any chance of turning Labour's (and his own) fortunes around. Yet strangely I am more optimistic about Labour's future today than I have been for some time. Why? Bizarrely, the tumultuous events on the world's financial markets in the past few days offer Labour a unique opportunity to stage a fight back and to put some clear red water between themselves and the City-friendly Tories. According to a Institute for Fiscal Studies the highest-earning 0.1% of the UK population enjoy an average annual income of £780,043. This is around 31 times higher than the national average income of £24,000. Given the present context, and given Gordon's commitment to fairness and equity, surely a national debate (led by the PM himself) about whether the very wealthy should contribute a bit more through the tax system would be most welcome. The public has watched on in horror and disgust at the City traders who deliberately bid down bank shares, bet on the failure of key stock and companies and even – it is suggested – spread false rumours in order to line their own already very deep and very full pockets. The debate should not be dominated by where the cut-off should be placed for any new tax (should it kick in at £150,000, £250,000 etc). Rather, it should be a debate about the principle of such a tax.

Talking about such issues could well be fertile ground for Labour and make life distinctly uncomfortable for David Cameron and his front bench. Cameron's Conservatives are made up of the "right kind of people", his people – privately educated and from backgrounds of immense wealth and privilege. Under Cameron, the Tories still believe that the role of government is to concentrate wealth and power in the hands of those who embrace their political, economic, and social views. For these reasons, Cameron would be reluctant to get into a debate about the super-rich and what they should or should not contribute via the tax system.

Brown should be bold. He has little to lose either personally or politically but both he and the nation have, potentially, a good deal to gain.

People need to look at the tax system in the round before criticising individual aspects of it. What those who decry the removal of the 10% starting rate conveniently forget is that - due to the tax credit system - it is the wealthy, not the poor, who will lose most from it.

Gordon Brown is conducting a live webcast at 7 pm tonight. Why not focus on the one issue increasingly dominiating the airwaves? Tell him what you think about the cost of the 10p income tax band cut on 5.3 million hard-working people, and ask him to fix it.

According to Frank Field "super rich" should pay a minimum of 10% more tax on any earnings over £150,000 (or give the same amount to a charity of their choice). Field suggest that such a move could raise £3.6bn a year.

What do you think? Personally I think it has real merit.

The prime minister vowed to take action on private equity chiefs in the pre-budget report later this year.

During a wide-ranging question-and-answer session with Mariella Frostrup, the TV and radio presenter, at the Labour party conference in Bournemouth, Mr Brown said: "Whenever there is a loophole that shouldn't exist we take action. Since 1997 we have closed a massive number.

"Sometimes it is very difficult to do so because you have lawyers and accountants who are always trying to find these loopholes.

"But on this issue of private equity I can assure you that we will do so."