Britain will immediately end freedom of movement for people from the European Union after Brexit on 31 October, a spokeswoman for Downing Street has said.
The spokeswoman said: "Freedom of movement as it currently stands will end on 31 October when the UK leaves the EU."
She added the UK government planned "tougher criminality rules for people entering the UK" as part of the new hardline stance.
"Details of other changes immediately on 31 October for a new immigration system are currently being developed," she said.
The change comes amid growing fears Britain is set to leave the EU without a deal in two-and-a-half months.
Around 3.6 million EU citizens already in Britain have been told to apply for "permanent settled status", under an interior ministry scheme started by Prime Minister Boris Johnson's predecessor Theresa May.
So far only around one million have signed up for the status.
Mrs May's government said in January that it would end free movement "as soon as possible" after a no-deal Brexit, but keep allowing EU arrivals "for a transitional period only".
Legislation drawn up to deal with the issue is stuck in parliament in the House of Commons gridlock over Brexit.
However, the Irish Government says Irish citizens will keep their rights under the Common Travel Area deal, which pre-dates EU membership.
What is the Common Travel Area
Irish and British citizens move freely and reside in either jurisdiction and enjoy associated rights and entitlements including access to employment, healthcare, education, social benefits, and the right to vote in certain elections.
The Common Travel Area pre-dates Irish and UK membership of the EU and is not dependent on it.
The two governments have signed a Memorandum of Understanding, reaffirming their commitment to maintaining the CTA in all circumstances.
Read more - Johnson tells Varadkar that Common Travel Area will remain after Brexit
Meanwhile, Mr Johnson believes the EU will blink first in the Brexit stand-off but acknowledged there would be "bumps along the road".
He has rejected demands for the recall of parliament following warnings that a no-deal Brexit would cause "incredibly serious" economic harm.
Mr Johnson will use face-to-face talks with Angela Merkel and Emmanuel Macron later this week to spell out his commitment to leave the European Union with or without a deal on 31 October.
He acknowledged there was "reluctance" in Europe about his demands for the backstop to be scrapped.
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"There may well be bumps in the road but we will be ready to come out on October 31st deal or no deal," Mr Johnson said during a visit to Truro.
"Now of course our friends and partners on the other side of the Channel are showing a little bit of reluctance at the moment to change their position.
"That's fine - I'm confident that they will - but in the meantime we have to get ready for a no-deal outcome.
"I want a deal. We're ready to work with our friends and partners to get a deal but if you want a good deal for the UK, you must simultaneously get ready to come out without one."
In a letter released this evening, Mr Johnson has written to EU Council President Donald Tusk outlining his opposition to the backstop element of the Withdrawal Agreement.
Meanwhile, Jeremy Corbyn, the British Labour leader, has said his party will do everything possible to stop Britain leaving the EU without a deal on 31 October.
He urged MPs that were "serious" about blocking a no-deal Brexit to bring down the government in a no-confidence vote and said Labour would form a time-limited government to avoid leaving without a deal.
He said: "It is the Conservative Party's failure on Brexit and its lurch to the hard right that has provoked the crisis our country faces this autumn.
"After failing to negotiate a Brexit deal that will protect jobs and standards, Boris Johnson's Tories are driving the country towards a no-deal cliff edge."
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Elsewhere, the Minister of State at the Department of Finance said the British government needed to be reminded of its "serious obligation" as core guarantors of the Good Friday Agreement.
Patrick O'Donovan's comments follow the leaking of a dossier prepared by civil servants at Westminster to The Sunday Times.
It warns of the impact of a no-deal Brexit, including fuel, fresh food and medicine shortages, as well as delays at airports, and a hard border.
Speaking on RTÉ's Morning Ireland, Mr O'Donovan said the document is only a month old, and that from the Government's point of view, there's no "good deal" to be had from Brexit – it is simply a case of how bad the deal could get.
He said the Government has been working on upskilling Revenue and bringing in additional staff, and encouraging businesses to engage with Revenue.
He said that if border checks are required, they should take place away from the border.
Brendan Howlin, Labour leader said Operation Yellowhammer is not a single assessment in time, but a process that has been in operation for many months.
Speaking on RTÉ's Today with Miriam O'Callaghan, he said the document looks at what is likely to happen, rather than what might happen.
