In 2007, the city had some 518,000 illegal immigrants or 6.9% of the 7.5 million population, the mayor said in an e-mailed press statement this earlier month, quoting new research from the London School of Economics (LSE).

The study also shows that there were about 725,000 foreigners in the UK illegally, an increase of 295,000 since 2001.

“This is a huge issue for the capital,” said Johnson, a former Member of Parliament who was elected as London Mayor May 2008.

“London is disproportionately affected, with more irregular migrants than anywhere else in the U.K.

“We need far tougher border controls to control the flow of people into our country,”

Johnson added.

“We should carefully consider the merits of an earned amnesty for long-term migrants to maximize the economic potential of these people so they can pay their way.”

In November, Johnson commissioned the London School of Economics research on the impact of immigration. The report will be completed in the next three months, he said.

But Boris is out of step with his own Conservative party and the ruling Labour Government, which has ruled out an amnesty.

There are an estimated 500,000 to 750,000 people in the UK illegally. According to an earlier ippr study, finding and removing half a million illegal immigrants would cost around £5 billion and take up to 20 years.

The ippr report also concluded that legalising those migrants and bringing them into the tax system would add billions in tax benefits to the UK economy.

What do you think? Would an amnesty be good or bad for Britain?

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