The Home Office has come under fresh criticism after it emerged that illegal immigrants have been approved for work in the security industry.

Hundreds of thousands of people who were vetted by the Security Industry Authority are now having their applications rechecked as a result of the news.

The SIA had not checked that applicants seeking approval to work in the sector were entitled to work in the UK.

The Sunday Mirror reported that illegal immigrants have been working at the Metropolitan Police, in Whitehall, and at ports and airports.

It estimated that 5,000 illegal immigrants have been employed in posts such as security guards and bouncers.

A Home Office spokesman said the SIA "took immediate action as soon as they became aware that some licence-holders had been employed illegally".

"From July this year, all new applicants have been granted a licence only if they are entitled to seek work in the UK," he added.

"Ministers ordered checks on all existing licence-holders and these will be completed shortly.

"Any individual found to be working illegally will have their licence removed and face removal from the UK."

But shadow immigration minister Damian Green said: "What is extraordinary about this latest Home Office fiasco is that we have been through this before.

"Last year the Home Office discovered it was employing illegal immigrants as cleaners in the immigration department itself.

"From these new revelations 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."

And Liberal Democrat home affairs spokesman Nick Clegg said that public confidence in the government's handling of immigration "will take yet another hammering".

"It is impossible to promote the merits of a fair and effective immigration system as long as the government mixes headline-grabbing populism with serial administrative incompetence," he added.