The UK government on Sunday announced increased fines for employers and landlords who allow migrants without papers to work for them or rent their properties, as part of measures to deter migrant arrivals.
The Conservative government, languishing in the polls ahead of a general election due next year, wants to stop illegal crossings of the English Channel in small boats.
The interior ministry said "illegal working and renting are significant pull factors" for migrants making the dangerous journey.
Civil penalties for employers will triple to up to £45,000 ($57,000) per worker, the ministry said in a statement.
Fines for landlords will rise from £1,000 per occupier to a maximum of £10,000, with fines for lodgers also increasing.
The fines will be higher for repeat offenders.
Landlords and employers are required to check the elegibility of their employees and tenants.
The new penalties will come into force in early 2024, according to the ministry, which said they were last revised in 2014.
"Making it harder for illegal migrants to work and operate in the UK is vital to deterring dangerous, unnecessary small boat crossings," Immigration Minister Robert Jenrick said.
- Barge controversy -
Prime Minister Rishi Sunak, who became leader last October, has pledged to stop the thousands of migrants crossing the Channel following an uptick in arrivals.
Last month his government passed a law, criticised by the United Nations, that bars asylum claims by migrants arriving via the Channel and other "illegal" routes.
It also mandates their transfer to third countries, such as Rwanda, but that element of the law has been bogged down in court challenges.
London also wants to reduce the cost of hotel accommodation for asylum seekers waiting for their claims to be processed, and has suggested the use of disused military bases, barges and even tents.
The Bibby Stockholm, a barge docked on the southern coast of England and set to house up to 500 asylum seekers despite local opposition, was expecting its first arrivals last week but has experienced delays.
Jenrick told Sky News on Sunday that the first asylum seekers would arrive on the barge "in the coming days" and assured that the facility is safe.
Also on Sunday, the main opposition Labour party said that if elected it would temporarily continue using barges and other infrastructure already in place while a backlog of asylum claims is tackled.
Labour's spokesman for immigration, Stephen Kinnock, said he was "confident" that if his party formed a government it would get on top of the backlog "within six months".