Johann Hari: The stakes are high, so don't gamble with the lives of the weak and the poor

If you refuse to choose the lesser evil, you don't get salvation, you get Michael Howard

I feel the hunger too. The craving to protest vote against the accumulated grievances of the past seven years is intense. Remember the cramming of more people into our prisons than ever before, the end to the right to a jury trial, the endless arms sale to fetid regimes, Blair's praise for the mass slaughter in Chechnya, the very existence of David Blunkett? There, waiting for you, is the ultimate comfort vote: the Liberal Democrats. No blood, no odour, just an ethical glow.

So why won't I do it? With a low feeling in my gut, I have to acknowledge that splitting the left vote will let the Tories in through the middle. If you refuse to choose the lesser evil, you don't get salvation; you get Michael Howard. Don't believe those who say it can't happen: it happened throughout the 1980s, when a majority of people (56 per cent) voted for divided centre-left parties and Thatcher ruled supreme. If enough Labour voters haemorrhage away, if the left is divided enough, the Tories can grab this election with a minority of the vote. They did it for 18 howling years.

Yet most of my friends believe the stakes are so low and the differences so small they can afford to protest vote. They stampede away from Labour, suspecting - like the veteran leftie Tariq Ali - that it is "pure sentimentality" to believe there are "substantive differences between the parties".

John Lennon - in 1979 at a time when most of the left thought Labour's leaders were a bankrupt band of sell-outs and charlatans, said: "The gap between the parties is far too narrow - but a lot of people live in that gap. It's the people I grew up with who will pay the price if you pretend there is no difference at all." I'm sticking with a Lennonist slogan for this election: Mind the Gap. Here are some of the policies that lie in the narrow space between Labour and Tory, the policies you are sliding on to the roulette table if you protest vote:

(1) The 1951 UN Convention on Refugees. Michael Howard's Britain would be the first democracy ever to withdraw from the Convention. For the first time since the Holocaust, Britain's policy would be openly to turn away people fleeing tyranny.

The BBC journalist Jeremy Vine recently asked David Davis, the shadow Home Secretary, whether he would turn away Aung San Suu Kyi - the Burmese pro-democracy leader - if she sought asylum in Britain after the proposed Tory quota was full. He was forced to admit she would be sent back into the poisonous embrace of the Burmese junta.

The international consequences of this policy are devastating. If the fourth largest economy in the world pulls out of the Convention, the right-wingers in every nation will point to Britain and ask, "Why not us?" As one UN official recently told me, "If Britain withdraws, the other democracies will fall like dominoes. The international architecture for dealing with refugees will be dead within a decade." It is no exaggeration to say the future of the world's refugees hangs on this election.

(2) Increases in the minimum wage. Labour will increase the minimum wage by 9 per cent year-on-year. Michael Howard - who was describing it as "a terrible mistake" until a few short years ago - will freeze it at the current level. The difference of a few pounds an hour, which is what it would add up to, might seem like "sentimentality" if you live in Kensington, but it makes a great difference if you are living on the poverty line.

(3) The reforms from the MacPherson Report. As Home Secretary, Michael Howard refused to launch an inquiry into the failures of the Metropolitan Police and their handling of the murder of Stephen Lawrence. Now, as Tory leader, he has campaigned against the recommendations of the MacPherson inquiry as "crazy political correctness". For example, it suggested the police should log the ethnicity of people they stop in the streets, to stop them harassing young black men. The Labour government agreed. Howard has called this "ludicrous".

The most powerful moment of the election was when Doreen Lawrence, Stephen's mother, challenged Howard for demonising the safeguards that prevent the police abusing black people. Howard was reduced to stammering, "I didn't know I was going to be asked about this." It was the lowest moment in a low campaign where Tory candidates blamed asylum-seekers for MRSA and the BNP leader accused Howard of "stealing our territory".

(4) Methadone prescription. This might sound like an odd or even trivial policy to include, but - like so many of Labour's silent progressive policies - it has massive ramifications. The Government has increased methadone prescription for opiate addicts by 40 per cent, and they are beginning to roll out heroin prescription for the most chronic users. The result? The number of people sleeping on our streets has fallen by two-thirds and burglary rates have plummeted, as they have in every country that chooses to help addicts rather than harangue them. Thousands of women and boys have been saved from selling their bodies for their next fix. The Tories will slash these prescriptions to pay for tax cuts and set these people on the road back to Cardboard City and crime, crime, crime.

There are dozens of small, day-to-day decisions like this where a Labour government will make a quietly progressive decision and the Tories will make a savagely reactionary one. Increased tax and spending, the Human Rights Act, SureStart centres for the poorest mums, redistributive tax credits for the poor, wind farms, Britain's place in Europe - they all hang in the Gap. Is it all "pure sentimentality"?

Go to to find the main anti-Tory force in your constituency is; you might be lucky and find it is the Liberal Democrats. If you are in Brighton, you can vote Green - they stand a serious chance of winning. But if you live in a Labour vs Tory seat and you refuse to choose the lesser evil of Labour, the beneficiaries of these policies will pay the price.

If Iraq was your breaking point, ask, as Robin Cook does, why the British poor should be added to the long list of collateral damage from the war. If your grievances lie in other failures, then vote Labour on Thursday and join a pressure group on Friday - from Liberty to Greenpeace to the Campaign Against the Arms Trade - to lobby them for change. With Labour, there is a chance it will listen; with Michael Howard, he will not. When the stakes are this high, are you prepared to play dice with the Britain's addicts, ethnic minorities, our poorest workers and the world's refugees?