Employers who hire people without the proper visas will be subject to a £45,000 penalty per worker for the first breach, rising to £60,000 if found to be repeatedly breaking the rules.
This is up from £15,000 and £20,000 respectively.
Landlords will also see fines increased to £5,000 per lodger and £10,000 per occupant if caught housing an illegal migrant, up from £80 and £1,000.
Repeated breaches will rise to £10,000 per lodger and £20,000 per occupier, up from £500 and £3,000 respectively. The crackdown was first announced in August.
Ministers argue that reducing the “pull factor of a promise of work and a place to live” for people considering crossing the Channel in small boats will help prevent smugglers.
But Labour has argued that “strengthening penalties must be combined with stronger enforcement action”.
Illegal Migration Minister Michael Tomlinson, said: “We are making great strides in our work to dismantle the business model of the evil people smugglers.
“But rogue employers and landlords who willingly allow illegal migrants to work for them and rent their properties undermine our efforts. It’s an affront to honest, hard-working people who play by the rules. “Illegal working enforcement visits ramped up by nearly 70per cent last year.
“By robustly cracking down on those who facilitate these illegal practices, we are providing a vital deterrent against making dangerous and unnecessary journeys to the UK. Carrying out the appropriate checks is simple, straightforward and a legal requirement – there is no excuse and those who don’t will face these stringent penalties.”
It is unknown exactly how many people are in the UK illegally.
A Greater London Authority report from 2020 estimated that between 594,000-745,000 undocumented people were living in the country.
The Home Secretary announced in December that there would be a wave of new restrictions on people coming to Britain, and their family members, in a bid to bring down legal immigration.
These included significantly hiking the minimum wage needed to obtain a visa.
Reforms to restrict care workers from bringing family members to the UK will come into force on March 11.
Measures requiring care providers to register with the Care Quality Commission if they are sponsoring migrants will start on the same date.
An increase to the minimum salary required for those arriving on a Skilled Worker Visa, from £26,200 to £38,700, will start from April 4.
The minimum income threshold for those bringing dependents to the UK on family visas will increase in stages starting on April 11. From this date workers will need to be earning at least £29,000-a-year to bring a family member from abroad - up from £18,600
No date for when the threshold will rise beyond £29,000 has been announced by Government.