Environmental version

"War destroys environment," say the greens, "don't bomb Iraq!"
Bush says "I don't know what you mean, I'll bomb Iraq
We wouldn't limit CO2, now this is nothing new,
So this is what we'll do, we'll bomb Iraq."

With uranium depleted bomb Iraq
We cannot be defeated, bomb Iraq
Children dying of leukaemia, the result of our mania
But we won't take the blame, ah - bomb Iraq

Destruction of the water supply, bomb Iraq,
Will cause even more people to die, bomb Iraq,
Our lifestyle depends on oil, to the victor goes the spoil,
Though in Hell we may boil, bomb Iraq.

We need to test new weapons, bomb Iraq
Who cares about inspections?, bomb Iraq
Our soldiers they need practice of all the latest tactics
So we'll test our new weapons, and bomb Iraq

Feb 15 verses

People on the streets say "Don't Bomb Iraq"
Pastors in churches pray "Don't Bomb Iraq"
If our leaders pay attention, it is just to mention,
It's still their intention to bomb Iraq.

Masses in their millions came out, don't bomb Iraq
"Not in our name" they did shout, "Don't bomb Iraq"
Blair says "I see your point of view, but this we've got to do,
Though your numbers aren't few, we'll bomb Iraq."

Bush and Blair put on their act, clap your hands
We must weed supposition from fact, don't clap your hands,
So many stories they tell us, trying hard to sell us
Reasons ever-changing to - bomb Iraq.

People of the world, they don't like -don't bomb Iraq
Threats of pre-emptive strike - don't bomb Iraq
If the bombs you stay, peace yet might win the day
List' to what we say - don't bomb Iraq

But yet we'll make you heed, don't bomb Iraq
No war for the sake of greed / Pay attention to real needs, don't bomb Iraq
Inspections are in place; attack and you'll loose face,
Of humanity show a trace, don't bomb Iraq

The 'Imperialist Hegemony' verses

And after Iraq let's bomb Syria, Bomb Iraq
Whip up more 'Axis of Evil' hysteria, Bomb Iraq
Our might knows no border, In search of a new world order;
Who comes next - after we - Bomb Iraq?

Don't forget Libia, Iran and Saudi - bomb Iraq
Any country that don't do what it ought-y, bom Iraq
France, clean up your act, lest you face our attack -
Who comes next - after we - Bomb Iraq?

[alternative tune "You cannae throw your granny off the bus" (she'll be coming round the mountain); some of the 'Bomb iraq' refrains may be omitted]

I think the song would be best sung among a group with individuals contributing their own verses, some made up on the spot.
I found it easier to compose my own verses (above) than to learn the ones already contributed to the threads. Also, a lot of the existant verses use the cliché of a war planned to distract the public's attention from failings elsewhere in the political arena, and I don't think that formula fits in this instance.
In practice, I would sing an eclectic mix of verses that I like best, not including all the ones I've offered about and despite what I said about formulas I do start with "If you cannot find Osama. ..."

Are there versions going around in other countries, in different languages?

I've made up several Irish-language verses too; 'bualadh bos' means 'clapping hands' , applause, and doesn't sound too unlike 'buille Bush', Bush's strike; 'buile Bhush', Bush's madness, 'Buail Bush' - defeat Bush. So for instance -
"Ní dhéanfar ar ár son é, 'buille Bush'" (It won't be done in our name, Bush's attack - repeated) - Eitleáin cogaidh ar an tSionainn, in ainneoin neodracht s'againn (Warplanes on the Shannon [airport], despite our neutrality] Ní dhéantar ...