Regardless of her killer's mental state, the murder of West Yorkshire Labour MP Jo Cox reflected the poisonous climate created by years of xenophobic overbidding and scapegoating of migrant workers by politicians and governments.

With the campaign for this week's referendum, this climate has become so loaded with fear and hatred that the murderer, who was otherwise considered as a "normal and helpful" person by his neighbours, thought it legitimate to turn his nationalist far-right infatuation into action. He grabbed two guns and a knife and went for Jo Cox, shouting "Britain first". Why? Probably just because she was known for supporting the refugee children who Cameron wanted to bar from entering the country!

Since then, we've seen a repulsive festival of hypocrisy over Jo Cox's dead body: the very same politicians who fanned the flames which prompted her killer to act, fell over themselves to shed tears over her fate and hail her "generosity".

The role played by Farage and his Ukip party in creating today's poisonous atmosphere is obvious. So, for instance, their latest campaign poster "Breaking point", showing an endless line of refugees who appear to be waiting to "invade" Britain. Never mind that this picture was taken thousands of miles away, on the border between Slovenia and Croatia. This is just another of Ukip's scaremongering lies about migrant workers, after so many on this and other issues since the beginning of the present campaign!

But although some Eurosceptic grandees of the Tory right, like Michael Gove and Boris Johnson, are now trying to distance themselves from Farage, for fear that he might undermine the Leave vote, they also have their share of responsibility in the climate that has cost Jo Cox her life. Indeed, since the beginning of the referendum campaign, the official Leave camp has been increasingly focusing its campaign on whipping up anti-migrant prejudices, using similar methods to Ukip.

But then, how could it be otherwise? This referendum was called by Cameron to contain the restlessness caused by Ukip in his own party, among right-wingers who were worried about losing their cushy jobs. Far from countering Ukip's crass anti-migrant demagogy, Cameron went along with it all the way. But then he had paved the way for it.

We haven't forgotten the years when, before the rise of Ukip in the ballot box, Cameron was peddling the myths of "benefit tourism" and "health tourism" by EU migrant workers, with the hysterical support of the Tory tabloids. There was a logic in this, which had nothing to do with the facts.

Before that, Cameron had been blaming the jobless and poor for being a burden on public services, when the real burden were the cuts which were imposed on them. Then he offered EU migrants as another scapegoat that could be blamed for the increasing collapse of the NHS and the new cuts in welfare provisions.

And during this campaign, we've seen Cameron at it again, reminding all and sundry that he remained a "Eurosceptic", and arguing that the best way to clamp down on immigration was to remain in the EU, which would allow him more control thanks to the "concessions" he "won" last year.

So, ultimately, both sides are barking up the same tree. Both represent the same past policies which, in the past, have involved a turn of the screw against us in order to make us pay for the bosses' and bankers' crisis. And both, one way or another, represent the same future policy of playing one section of our class against another - "British" against "migrants" - in order to better undermine our ability to fight back.

Their referendum is a classical case of "heads I win", "tails you lose". In fact, media magnate Rupert Murdoch, who certainly knows how to play the political institutions of the capitalist class to his advantage, provides a perfect illustration of this. On the one hand the English edition of Murdoch's the "Sun" came out with a strident pro-Leave headline. But, in Scotland and Northern Ireland, the "Sun" never carried this headline... no doubt because it wouldn't have been very popular. Meanwhile, another of Murdoch's papers, the "Times" was siding squarely with the Remain camp! "Heads I win", "tails you lose": the Murdochs of this world always win at their political games!

This is why we, workers, should have nothing to do with this fake choice between two ways of hanging ourselves, while dividing and weakening our collective strength. The only way forward for us, workers, is to prepare ourselves to fight our own "enemy within" - the bosses here, their government and their system - by uniting across all the divisions that the capitalists would like to create within our ranks, and across all nationalities!