The year 2013 will go down as the one when British attitudes to immigration underwent a profound change.

In England at least, xenophobia has come in from the cold. Those advertising lorries cruising London boroughs calling on asylum seekers to "Go Home" were the most obvious manifestation of the change. But the whole manner in which immigration is discussed in Westminster has altered. "Migrant" has almost become a term of abuse.

The big story this week is that tens of thousands of Romanians and Bulgarians are preparing to invade Britain in the New Year to live the life of Riley on £71 a week Jobseeker's Allowance. Immigrants are routinely demonised in the UK press. "Romanian Big Issue seller who stole from blind pensioner living in £250,000 house", read one recent headline. It is assumed that, come January 1, Romanian migrants can fly in and begin a cushy life on benefits.

What is not reported is that all EU migrants have to pass a stringent "habitual residence test" and answer 100 questions about their ability to support themselves before they arrive in Britain. Not content with that, the UK Government this week rushed through legislation to deny all benefits to EU incomers from Romania and Bulgaria for three months. A leaked Home Office document suggested Teresa May intends to cap EU immigration to no more than 75,000 - a move that will put Britain on a collision course with Brussels, since free movement of labour is one of the founding principles of the EU.

The Government's Immigration Bill includes measures to force landlords to check on the immigration status of their tenants and make migrants pay for NHS treatment. This means people who were not born here, and even second generation immigrants who were, may have to carry what are effectively identity cards to prove they are not illegals.

"We are taking direct action to fix the welfare and immigration systems so we end the something-for-nothing culture", said Prime Minister David Cameron yesterday. "Accelerating the start of these new restrictions will make the UK a less attractive place for EU migrants who want to come here and try to live off the state."

Note the words: EU migrants; something for nothing; Living off the state. These phrases are not accidental. They have been deployed deliberately to chime with what the Government believes are the attitudes of the average British voter. According to YouGov, only 33% of Britons believe giving EU citizens the right to live and work here is a "good thing". Labour reads the same polling results, which explains why Yvette Cooper's response to this week's benefit clamp has been to attack the Government for not acting sooner. Former Labour Home Secretary Jack Straw says his Government made a "spectacular mistake" by allowing EU migration.

When did you last hear any leading politician in Westminster argue migrants are a positive benefit to the economy? A long time. The presumption is migrants are a burden on the state and the taxpayer. Yet nothing could be further from the truth. The vast majority of EU migrants come to Britain to work and are highly productive. They contribute annually about 2% of UK GDP. And we need more of them, not less. If Britain is to solve the "ageing population crisis": then we are either going to have to start having very large families, or else increase immigration.

Scotland's population is ageing more rapidly than England's and, according to the Institute For Fiscal Studies, this would create a financial black hole for an independent Scotland. The IFS reported last month that because of this shortage of workers, taxes in an independent Scotland might have to rise by up to 8% to balance the books. What the Institute did not fully consider was the possibility that increased immigration after independence could substantially alter the picture here. The SNP, to its credit, is the only party in Britain that appears to appreciate the economic benefits of inward migration. Indeed it is the only party in Britain that actually argues for open borders and for increased immigration.

And there is a very good reason. Immigrants are invariably young and they generally have larger families than Scots. Indeed, much of the dramatic increase in Scotland's population in recent years - there are more Scots than ever before in the nation's history - is down to immigrant families settling here from countries like Poland. Look at the number of Polish shops in the high street, the increase in attendance at Catholic churches; the appearance of Polish language books in libraries.

This has been to the benefit of Scotland and has caused virtually no racial tension. Polish immigrants, according to the Economist magazine, are generally over-qualified for their jobs in Britain. Immigrants are invariably blamed for bringing crime to these shores. Yet, according to the London School Of Economics, areas of high immigration in the UK have seen a decline in crime and violence.

As for benefit tourism, EU immigrants use the NHS less than Britons do. When did you last see a headline saying that? Or that education achievement is higher among immigrants than among the native population. Or that immigrants make a greater fiscal contribution than Britons because they depend less on the state and work very hard. Nor can immigrants be blamed for the failure to build housing in Britain.

Hypocrisy compounds the moral offence against EU migrants. After all, it was Conservative Prime Ministers Margaret Thatcher and John Major who urged the EU to press ahead with enlargement in the 1980s and 90s. Mrs Thatcher wanted to absorb Eastern European countries to weaken the then Soviet Union. John Major wanted rapid expansion to reduce the dominance of Germany.

This is why EU politicians get so annoyed at British rhetoric. EU Commissioner Laszlo Andor says Britain is becoming "the nasty country of Europe" and he has a point. It was always clear free movement within the community would imply reciprocal access to benefits across the EU. It is illegal to discriminate against citizens of member states - anywhere. To deny benefits to EU migrants or refuse to admit them when they have jobs to go to would challenge a fundamental principle of the single European market. Yet a majority of Conservative backbench MPs appear to want to go down this road.

In the New Year we are going to hear more attacks on EU migrants in the run-up to the European elections in June. The Conservatives and Labour are both running scared of the UK Independence Party. Free movement is one of the terms of UK membership Mr Cameron has pledged to "renegotiate". If he doesn't get it, then he will presumably call for Britain to leave the EU in the in/out referendum set for 2017.

Which puts into perspective the claim Scotland will be ejected from the EU if it votes Yes. Britain as a whole could be moving to an exit to keep those nasty foreigners out.