In his speech announcing the measures Tory leader Michael Howard made clear that he saw Britain's "lax" immigration system as posing a potential security threat, as he painted a picture of a nation under siege.

"We face a real terrorist threat in Britain today - a threat to our safety, to our way of life, and to our liberties. But we have absolutely no idea who is coming into or leaving our country. There are a quarter of a million failed asylum seekers living in our country today. No one knows who they are or where they are. To defeat the terrorist threat we need action not talk - action to secure our borders."

Both the Tories and Labour claim to be addressing the public’s “legitimate concerns” about immigration. But if we examine the terms of the debate over asylum and immigration, how well the debate is informed by the facts, the role played by politicians and the effects on society as a whole, a rather different picture is revealed.

The immigration debate is driven for the most part by the tabloid press. But according to Roy Greenslade, a former editor of the Daily Mirror, the tabloids "don't seek to inform their readers. They don't try to be fair, let alone balanced. They don't respect journalism's first requirement: to tell the truth. They set out to mislead and distort. They whip up the mob. They appeal to the basest of human instincts. The Daily Express ran 22 front page articles in a month about asylum-seekers, many of which stretched facts to breaking point. Its stablemate, the Star, ran a remarkable story which alleged that Somali asylum-seekers had stolen, killed and eaten donkeys from Greenwich royal park. There wasn't a scintilla of proof for this nonsense and you could laugh it off if it didn't form part of a pattern of far-fetched stories guaranteed to incite racial hatred. Some broadsheets have been infected by this kind of prejudicial journalism too. Test the facts in many Sunday Times stories and they just don't stand up. The Sunday Telegraph ran a story which claimed that six councils had banned schools from giving their pupils hot cross buns in order to avoid criticism from Muslim students. It was a totally false story which fomented racial tension. In similar vein, the Sun ran a front page which alleged that eastern European asylum-seekers had killed and eaten swans on the Thames. Again, there wasn't any evidence for this story - another in a sad catalogue of fakes. I've lost count of the scare stories about Britain being swamped by asylum-seekers, every one based on figures supplied by Migration Watch, a small organisation which happily provides guesstimates to journalists who then present them as fact."

The campaign of disinformation Greenslade describes has real and wholly predictable consequences. A poll conducted by MORI showed that on average young people believe the UK takes 31% of the world's refugees and asylum seekers (actual answer 1.98%), with only 4% correctly selecting the right figure. Only 19% of young people said they would be welcoming to asylum seekers/refugees in their community, compared with a mere 26% of adults. This is in spite of the fact that Britain’s is the world’s fourth largest economy and the vast majority of asylum seekers come from the most violent, dangerous and repressive places on earth. In 2003, the highest number of asylum applications came from people fleeing places like Somalia, Iraq, Zimbabwe, Iran and Afghanistan.

In this climate it should hardly have been surprising when The Observer (one of a small minority of trustworthy papers on the subject) reported last weekend that "violence against asylum seekers and ethnic minorities is more widespread than ever". Some particularly gruesome murders were mentioned in the report. Kalan Kawa Karim, an Iraqi asylum seeker, was beaten up and left to die while walking home after a night out in Swansea. Isa Hasan Ali, an Afghan asylum seeker, died after being beaten by a gang in a Southampton park. Firsat Dag, a Kurdish asylum seeker, was knifed while walking through Glasgow's Sighthill housing estate. And in one of the most shameful cases, Johnny Delaney, a 15-year-old Gypsy, was beaten to death at a playing field in Ellesmere Port.

Needless to say that these real-life killings of members of ethnic minorities by British nationals received far less tabloid attention than the fictional accounts of foreigners mistreating British livestock; a fact which neatly summarises the value systems of the newsrooms in question. One can imagine few barriers to full front-page coverage had the victims been British and the perpetrators been asylum seekers or gypsies. Even the customary obstacle of telling the truth might have been surmounted in such an instance.

Nor should it have been surprising when an ICM poll for The Guardian last week revealed that more than half of Britain’s members of ethnic minorities have been subjected to name-calling or verbal abuse, or that one in five had considered leaving Britain because of racism.

Given these unpleasant statistics one might hope that the relentless publication of "far-fetched stories guaranteed to incite racial hatred" in the press would attract some attention from the authorities. After all, the law clearly states that "a person commits an offence if he publishes or distributes written matter which is threatening, abusive or insulting, in a case where, having regard to all the circumstances, hatred is likely to be stirred up against any racial group in Great Britain by the matter or words in question." In fact, faced with a rising tide of prejudice and all the implications for public order and social cohesion that entails, politicians have sought not to counter the bigotry, but to pander to it.

At last year's conservative conference the Shadow Home Secretary David Davis said that immigrants were placing a burden on housing, health, education and public services in areas where that burden was already heaviest. In 2002 the then Home Secretary David Blunkett said that asylum seekers were "swamping" some British schools, mirroring Margaret Thatcher's controversial comment about Britain being "swamped by an alien culture". Despite criticism from the Campaign for Racial Equality, which described the remarks as "hugely emotive", Blunkett was unrepentant, insisting that the children of asylum seekers should be taught in separate "accommodation centres".

The notion of immigrants and asylum seekers being a "burden" on the state completely contradicts the government's own evidence. A recent Home Office report shows that people born outside the UK, including asylum seekers, contribute 10% more to the economy in taxes and national insurance than they consume in benefits and public services. Instead of fully realising this potential contribution the Government withdrew asylum seekers' right to work in June 2002, a couple of months after Blunkett made his infamous remarks. If the "swamping" reference was aimed more towards the cultural pressures of mixed schooling one might ask why Blunkett chose not to examine how the racist press had exacerbated those pressures, but to stigmatise foreign children instead.

The policy of appeasement adopted by both main parties is best summed up by an election campaign poster recently released by the Conservatives which reads, "Are you thinking what we're thinking? It's not racist to impose limits on immigration". Of course, the Tories would have some difficulty finding anyone who actually advocated unlimited immigration. But the real point here is to reassure anyone harbouring ill-informed prejudices that they remain firmly within the bounds of respectable opinion and that the Tories share their concerns. Both the voter targeted by the advert and the Conservative Party are offended more by their being accused of racism than by the reality of racism itself. Similarly the Prime Minister has said that "the public are worried about this, they are worried rightly, because there are abuses of the immigration and asylum system". However, the lying hate campaign pursued by the press, and the serious effects it has on the welfare of minorities, is somewhat less likely to be the subject of Tory campaign posters or reassuring statements from the Prime Minister.

The dynamic is one that has been played out to varying degrees across the world and throughout history on countless occasions. Prejudice and hatred is whipped up against a vulnerable minority. The authorities either stand back or actively pander to these prejudices, claiming to be addressing “legitimate concerns” and thus lending prejudice an air of respectability. These forces combine to create a climate in which abuse and violence can flourish. The familiarity of the story is profoundly depressing. As is the prospect that only those observing from the vantage point of history will recognise the pattern of events and behaviour unfolding, and wonder despairingly how a society where such things occur could possibly consider itself civilised.