5,000 illegal immigrants working as security guards in UK's most sensitive buildings

In yet another Government blunder, the Home Office has allowed the immigrants to take up posts at ports and airports - and even at Whitehall - despite having no legal right to be in the country.

And checks on the man who is in charge of guarding Gordon Brown's prime ministerial car against terrorist booby-traps revealed he was in the country illegally.

The Security Industry Authority (SIA) said it was not its job to even ask applicants seeking jobs protecting the public if they were illegal immigrants.

The only checks carried out were on a person's past behaviour or for any criminal record.

Since the situation came to light in July, officials admitted as many as 5,000 illegal immigrants have been given SIA licences over the past three years. It is feared they also include up to six people working at the Metropolitan Police.

The latest fiasco follows revelations last year that the Home Office had itself employed illegal immigrants on at least seven separate occasions.

It employed the workers both directly and indirectly, including five Nigerians who were caught working as cleaners within days of John Reid taking charge of the department last May.

Shadow Immigration Minister Damian Green said: "It looks like no effective action was taken to check who has access to some of the most sensitive buildings in this country.

"It looks like the Home Office is still not fit for purpose."

A Home Office spokesman said: "From July this year, all new applicants have been granted a licence only if they are entitled to seek work in the UK.

"Ministers ordered checks on all existing licence-holders. Any individual found to be working illegally will have their licence removed and face removal from the UK."

• More than eight out of ten Britons want a "substantial" cut in immigration levels, a poll has revealed.

Some 85 per cent said migration is putting too much strain on public services, including hospitals.

The findings of the YouGov poll, carried out for Migrationwatch UK, will alarm Ministers, who last week were forced to admit they had underestimated the number of foreigners working in Britain by 300,000.

The survey found only 35 per cent of those questioned believed immigration has contributed positively to the UK economy.

Nearly half, 48 per cent, said it was Government policy rather than worldwide trends which was responsible for the increase.

The Metropolitan Police confirmed that some of its contract staff had been revealed as suspected illegal immigrants during the review of licences granted by the SIA.

The force refused to say what jobs they had been undertaking, or how sensitive the positions were.

A spokeswoman said: "On April 4 we were informed that a number of people working for a company contracted to the MPS were the subjects of an immigration investigation.

"They were removed from MPS work and suspended by the contract company until the Immigration Service investigations were completed.

"The company involved was working closely with the Immigration Service to establish whether any immigration offences had been committed."