By Dominic Casciani BBC News Online community affairs reporter

What are the facts about immigration? BBC News Online looks at the current debate. Figures from Migration Watch UK, a new group led by a former diplomat and an Oxford University demographer, predict more than two million people will arrive in the UK every 10 years for the foreseeable future.

Not surprisingly, the figures have dominated headlines amid the continuing debate over asylum, immigration and race relations in the UK.

According to the government's own figures, the UK has the "third largest foreign population and labour force in the European Union", around 2.2m people.

No one disputes that immigration to the UK has been increasing since the late 1990s. The problem is it's almost impossible to agree by how much. So how does Migration Watch UK reach its conclusions?

We start from the belief that the scale of net inward migration is now so great as to be contrary to the interests of all sections of our community

Migration Watch UK

The most up-to-date official statistics reveal that 125,000 people settled in the UK in 2000.

Groups such as the Immigration Advisory Service say that sounds a lot, but it represents less than a third of one percent of the UK's population.

Migration Watch UK then adds a further 60,000 to this figure to account for asylum seekers who enter the UK but "disappear".

The group then makes a number of further assumptions. Firstly, it estimates that there could be some 35,000 more people from outside the European Union who come on a visitor's visa and then never leave.

It then calculates that there are at least another 25,000 who arrive at these shores "clandestinely", for instance by hiding in a lorry crossing the English Channel.

Whether this is a double-counting of asylum seekers is not clear.

Official predictions

The government's own figures are completely different to those of Migration Watch UK.

It says that there are no figures for undetected migration so predictions and calculations are impossible to make.

Its prediction for net migration to the UK from 2003 onwards is 135,000 a year. It does indeed agree that there will be an extra two million arrivals - but only by 2021.

The Home Office says that Migration Watch UK's figures should be treated with "considerable caution".

For its part, the Immigration Advisory Service, the main expert body dealing with the issue on a day-to-day basis, says today's predictions are little more than "idle speculation".

Economic arguments

So this then brings us to the question of absorption. Migration Watch UK says that there is "no economic case for large scale inward migration".

This is something that numerous academics and the government reject.

The UK's population is getting older, meaning that more working age people are needed to prop up the world's fourth largest industrial economy.

Secondly, there is a current shortage of highly-skilled people in key sectors such as the NHS, public services and the IT industry.

Thirdly, if the UK's population becomes more highly skilled and educated, there will be more and more jobs that people do not want to do. All of these factors have come together to create immigration demands.

One study by the University of Swansea predicts that we need to increase immigration by a fifth to protect prevent a population decline and subsequent economic crisis.

Some of this thinking is already filtering down to government which is changing the entry rules to meet the needs of the job market.

Which brings us to the final question about Migration Research UK's predictions: Irrespective of the exact figures, how will it go down with the British public?

In May BBC News Online published a major survey of public attitudes on race and immigration issues in the UK.

Asked whether they believed that immigrants found it easy or difficult to integrate in the UK, some 61% of all respondents said difficult. The figure remained largely consistent across all ethnic groups.

But on the question of whether or not immigration was a good thing, the numbers differed quite dramatically.

Some 47% of white respondents said that immigration had damaged Britain with a quarter saying they did not know.

Approximately a third of black respondents and Asian respondents also said they did not know - indicating the uncertain nature of the current debate on immigration to the UK.

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