By Dominic Casciani BBC News Online community affairs reporter

An immigration pressure group has warned that London and south-east England face a crisis in public services unless ministers cut the arrival of asylum seekers.

Sir Andrew Green, head of Migration Watch UK, said it was time to stop "ducking the issue" that mass immigration was damaging services in the capital and even the position of settled minorities.

You get on the Tube and you can barely move ... London is stuffed with people. Sir Andrew Green, Migration Watch UK

The former ambassador said Migration Watch's research suggested two-thirds of those who enter the UK settle in London and south-east England, most of them illegally.

Refugee campaigners have rubbished the figures as speculative estimates - saying the real crisis was the government's failure to improve asylum decision making and integration of those settling in the UK.

"There are hundreds and thousands of asylum seekers who were refused [permission to stay] who are living illegally in Britain, mostly in London," Sir Andrew told a London Assembly hearing.

"These flows are likely to continue and increase and there will be an impact on London's services."

Sir Andrew said the NHS in London had no way of working out who was eligible for services and the London Assembly should support the introduction of "entitlement cards".

Disputed figures

Migration Watch UK estimates immigration has pushed up London's population by approximately 600,000 in 10 years.

You can spend a lot of time counting the figures [but] the issue is how you manage the migration system Nick Hardwick, Refugee Council

Official statistics say the city's population has only grown by half that amount and remains below both predicted trends and the historic post-war high of 8.4m people.

Migration Watch UK's predictions on immigration have been criticised by asylum rights campaigners and the government alike.

Sir Andrew told the assembly hearing his organisation was non-political.

But he accepted some of its supporters were more concerned with the implications of immigration on British culture.

He accepted statistics show asylum seekers who work contribute to the economy - but argued the benefit was largely negligible.

He said: "You get on the Tube and you can barely move. London is stuffed with people. Under the present regime the numbers are going to keep going up and up and up."

Figures 'baseless'

Nick Hardwick, chief executive of the Refugee Council, rejected the figures as baseless.

He said: "The figures don't take account of those who leave the country. It's disingenuous for Sir Andrew to describe Migration Watch UK as neutral."

Mr Hardwick said the real crisis was the government's failure to manage migration.

If more resources were put into fair and speedy decisions, said Mr Hardwick, more asylum seekers would be recognised as genuine - and the machinery to deport false applicants would also improve.

Instead, the system, especially the national dispersal programme, was chaotic and reinforced suspicions about asylum seekers.

Mr Hardwick said: "In London the Refugee Council has 5,000 people in short-term emergency accommodation. The idea was that they would be there for a few days but they have been there for months and in some cases years.

"That's a completely unplanned impact on those neighbourhoods and public services."

In many cases asylum seekers dispersed to other regions were returning to London because it was the one place they could be guaranteed adequate support such as translators, English tuition and legal advice.

"You can spend a lot of time counting the figures and people will still argue over them. The issue is how you manage the migration system," he said.