Businesses that employ illegal workers will be hit with “the full force of government machinery”, immigration minister James Brokenshire has warned.
He said “rogue employers” who give work to illegal migrants were denying UK citizens jobs, driving down wages and gaining an “unfair advantage”.
The Times says immigration officers are to carry out raids on cleaning firms, building sites and care homes.
But Labour’s Yvette Cooper said the Home Office should “still do more”.
BBC political correspondent Robin Brant said ministers were trying to “enhance” practical measures to combat illegal workers, rather than bring in new measures.
How many people work here illegally?
A London School of Economics study estimated the UK had 618,000 “irregular” residents, but campaign group Migration Watch said the figures is closer to 1.1 million.
What is the government doing?
Immigration Enforcement teams will carry out more raids, along with bodies such as HM Revenue Customs, the Gangmasters’ Licensing Authority and Health and Safety Executive taking part.
What happens to employers of illegal workers?
Employers can be fined up to £20,000 per person for employing illegal workers. Employers who knowingly employ an illegal worker can be jailed for up to two years.
Would Calais migrants really be better off in the UK?
What happens to UK asylum seekers?
Mr Brokenshire said: “Experience tells us that employers who are prepared to cheat employment rules are also likely to breach health and safety rules and pay insufficient tax.
“That’s why our new approach will be to use the full force of government machinery to hit them from all angles and take away the unfair advantage enjoyed by those who employ illegal migrants.”
Shadow home secretary, Ms Cooper said the government should extend the Gangmasters’ Licensing Authority – a public body that works to stop worker exploitation – and to “make exploitation a crime”.
“Exploitation hurts everyone – those who are working hard and being exploited, other workers whose pay and jobs are undercut, and responsible employers who are undermined,” she added.
By Robin Brant, BBC political correspondent
It’s not new but he’s hammering away at the message.
James Brokenshire is targeting illegal foreign workers, employers giving them work and the Brits who’ve just elected a Tory government.
To the foreign workers it is an echo of Theresa May’s words last week: that the streets of Britain are not “paved with gold”.
To the care home and cleaning company workers who’ll face more unannounced visits it’s an echo of the measures announced last week threatening landlords who house illegal workers with longer prison time.
To the voters who see chaos in Calais on the TV it’s yet more evidence, he hopes, that the government is trying its best.
A 2009 study carried out for London Mayor Boris Johnson estimated that the UK had 618,000 “irregular” residents, with London accounting for about 70%. The campaign group Migration Watch says a figure of 1.1 million is “more plausible”.
The Organisation for Economic Co-operation and Development estimated in 2011 that the use of illegal immigrants represented 1% of total employment in the UK.
In 2013, a BBC investigation found two-thirds of fines imposed on employers of illegal workers over a five-year period had been uncollected in the past five years.
Last week, it was announced landlords in England would be expected to evict tenants who lose the right to live in the UK, or potentially face prison.
Mr Brokenshire’s comments follow a call from Foreign Secretary Philip Hammond for EU laws to be overhauled to ensure people coming from Africa to Europe could be returned to their home country.
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