The Big Question: Should illegal immigrants be granted an amnesty in Britain?

How many illegal immigrants are there?

No one doubts that there are hundreds of thousands of foreign nationals living and working "under the radar" in Britain, but it is difficult to be much more precise. Even Dave Roberts, a senior official in the Immigration and Nationality Directorate, recently confessed he hadn't the "faintest idea" how many illegal immigrants were in the country.

The Home Office has put the number at between 310,000 and 570,000, producing a best estimate of 430,000, or 0.7 per cent of the population. The total includes foreigners who entered the country clandestinely, those who overstayed visas and failed asylum-seekers who have not left. The numbers do not take into account those seeking political asylum whose applications are currently being processed. Migrationwatch which campaigns against mass migration, claims the figure could be as high as 870,000. According to one estimate, 39 per cent of illegal immigrants came from Africa, 28 per cent from Asia, 15 per cent from Europe, 11 per cent from the Americas and 7 per cent from the Middle East.

Why has this issue come up now?

The new Immigration Minister, Liam Byrne, refused to rule out the prospect of an amnesty when he appeared before MPs in the Commons. Both the Home Office and Downing Street moved speedily to defuse the inevitable row, insisting there were "no plans for an amnesty", but the genie was out of the bottle. The Tories claim it could lead to a massive and uncontrolled increase in migration, while the Transport and General Workers' Union backed an amnesty, calling on ministers to distinguish "between deporting the few who commit serious crimes and allowing the many undocumented migrant workers to remain".

How would an amnesty work?

People in the country illegally would be invited to come forward in return for receiving a renewable work visa. They would be expected to supply biometric information, such as fingerprints or iris scans, for identity cards (which all foreign nationals will shortly be expected to carry). They might be expected to demonstrate they have been in regular work and certainly would have to prove they have no criminal convictions. David Blunkett, the former Home Secretary, gave a clue yesterday to the thinking in the Home Office. He said it would be impossible to have an amnesty without identity cards and a clean data base. The Government offered an amnesty three years ago to 15,000 families - about 50,000 people - who had sought asylum before the year 2000. Two earlier amnesties, in 1993 and 2000, allowed another 53,000 people to settle in this country.

Would there be any benefits?

The Institute for Public Policy Research (IPPR) calculates that the Treasury could expect an annual windfall of £1bn as a hidden army of workers are brought into the tax system. They would gain the rights other UK employees enjoy, such as the minimum wage and safe working conditions. At a stroke the country would also be relieved of the mammoth task of deporting illegals, which could take 20 years at current removal rates and cost the country more than £4bn. Were they deported, acute shortages of cleaners, care workers, building labourers and restaurant and hotel staff would develop.

What about risks?

The most obvious is of creating a massive "pull factor" among migrants from developing countries. Public services, particularly in the South-east, could also come under increased pressure. Giving them permission to remain in Britain would also allow them free movement around the European Union, which might not be well received in other EU countries. Some would also argue that an amnesty is less preferable to a managed migration programme which tailors flows to economic needs. Giving a Ukrainian labourer permission to stay would not help fill a chronic need for for, say, nurses or information technology specialists.

Have amnesties been granted elsewhere?

Spain, widely considered to be in the front line of illegal immigration, has offered five amnesties. In the most recent,an estimated 700,000 illegals registered with the scheme. It is also thought to have raised €1.5bn in taxes in its first year.

Critics counter, however, that the fact that Spain has been forced to offer so many amnesties is proof that regularisation schemes attract mi- grants. Italy has also offered six amnesties, France and Belgium two each.

In 1986, the US government offered a regularisation programme to illegals in the country for at least four years. But its results were mixed, with little impact on the waves of illegal immigration to the United States.

Today there are an estimated 11 million illegal immigrants in the US, the majority from Mexico and central America. Controversial proposals from President Bush to offer renewable work permits to many of them are dividing political opinion in the US.

What are the political dangers?

For more than three decades immigration has been a background issue in British politics.The term "asylum seeker" has become synonymous with "illegal immigrant" in the public mind. Since the September 11 attacks, the issues of terrorism and immigration have also become intertwined for many voters.

It is a potentially toxic combination and ministers are aware that offering an amnesty to 500,000 foreigners could provoke a backlash with the public. Following the foreign prisoners fiasco, which cost Charles Clarke his job as Home Secretary, the Government is wary, knowing that granting an amnesty would open them to the charge of rewarding migrants who took advantage of government failures to police Britain's borders.

Would Britain benefit?

Yes...

* It would bring in huge tax revenues for the Exchequer

* The burdensome logistical exercise of deporting illegals could be avoided

* An amnesty would give migrants and their families the opportunity to integrate better into British society

No...

* It would be tantamout to rewarding law-breakers

* The country's public services would be placed under unbearable strain by the sudden increase in numbers using them

* Granting an amnesty to undocumented workers would act as a magnet to hundreds of thousands of others around the world