Johann Hari: This is the chance to go down with all guns blazing

This is a great week for Gordon Brown. You've lost. It's over. The next general election will result in a Conservative victory. So you have two years now – two liberated years – to be the Prime Minister you always wanted to be.

Of course it must be tempting for him to say: but couldn't I claw it back? Yes, he can point to the fact that electorates across the world are more volatile than ever. Voters now roam across the savannah of politics capriciously. In 2004, the Americans flocked to Bush big-time; in the 2006 mid-terms they elected the Democrats with a landslide. Last year the French love-bombed Sarkozy into office; this year the Socialists have a big lead.

And, yes, Brown can rightly reason that David Cameron is little more than a corporate spin-doctor, hiding a startlingly right-wing agenda behind caring rhetoric. Cameron's policy review actually recommended US-style deregulation of the mortgage market so that sub-prime mortgages could be sold to the poor – just before that policy caused the world economy to tank.

None of this can stop 2010 turning into a national Brown-out. He has the right-wing press against him, and even the liberal press is falling for Cameron's spin. Meanwhile, the country has watched Brown take out his 10p razor and commit electoral self-harm too often. Nor is the idea of using that razor to cut the Gordian knot by switching leader any better: the electorate would be appalled by a Prime Ministerial misery-go-round and kick Labour out anyway. Besides, who would want to be PM for a year and then lose?

So Brown now has an energising choice. You can be an honourable failure who goes down fighting for the causes you always believed in, or you can be an amoral failure who dies with an immigrant-bashing belch. Over the next few weeks, choose three or four progressive causes you can push through before 2010 that the Tories would find it hard to reverse. Go through the black marks against New Labour in the history books, and put some of them right. Go down fighting.

Let's start with the cause that drove you into politics – opposing extreme inequality. Before the 1997 election, you vehemently argued against Tony Blair, saying we should have a higher top rate of tax for the wealthy. You lost then. Go back to it now. Even after a decade of mild redistribution, 74 per cent of the British people think the gap between rich and poor is too great. So make the wealthiest pay a 50 or 60p tax rate – like even Thatcher did in her early years – and use the money to increase tax credits for the poorest. Do a string of press conferences with the once-poor parents who are £4,200 a year better off as a result of the credits, and ask how they feel when they hear David Cameron compare them to the failed nationalised industries of the 1970s.

Or how about global warming? Britain's carbon emissions are now slightly higher than in 1997 – far higher if you include emissions from the manufacturing we have shipped to China. Brown has set us on a track to even more warming by championing airport expansion and coal. But before he goes, he can start to put it right. At the moment, two of the most popular destinations from Heathrow are, shockingly, Manchester and Edinburgh. So use your last few gallons of power to treble the cost of all domestic flights – and use every penny to bring train fares down. Make it economically rational to make the environmentally rational choice. And while you're at it, price SUVs off the road with fatter road taxes, with the cash again flowing on to our train tracks. Cameron would have to choose between backing you, or tacitly conceding his greenery was a cynical exercise in rebranding.

Then there is the greatest black mark on Labour's record (and, more trivially, on my own as a commentator). Nothing Gordon Brown can do now will bring back the 650,000 Iraqis who have died as a result of the invasion. But he can do something for the 5 million who have been driven from their homes. At the end of the Vietnam war, the US felt obliged to take in 800,000 refugees from the country they had destroyed, and to pay for the resettlement of others elsewhere. (Those refugees, by the way, went on to enrich America massively.) Brown should issue an apology to the Iraqi people on behalf of Britain, and fly in a fair share of the Iraqi refugees rotting and penniless in camps in Syria and Jordan as the most minimal act of compensation. Instead, we are actually deporting many of the Iraqis who make it to our shores, on the grounds that it is "safe" there, even though the US aerial bombing campaign has been stepped up once more in the past few weeks.

This apology could also have a jolting effect on the US presidential race, putting America's closest ally into alliance with Barack Obama. Cameron could hardly complain that Brown was junking the tradition of British leaders not interfering in US politics: he lovingly introduced the hard-right John McCain as "the next President".

If you are going to lose, Gordon, lose with style. Lose as the man who said Labour is "at our best when at our boldest". But please, don't lose like this – paralysed and pitiful and pandering to people you detest.

j.hari@independent.co.uk