Foreign criminals and illegal migrants who claim to be victims of modern slavery face deportation under a clampdown on abuses of the anti-trafficking laws.
Suella Braverman, the Home Secretary, said the new rules would allow ministers to deport any foreign criminal who has served more than a year in jail or has been convicted of serious offences even if they claim they are victims of modern slavery.
Any migrant who makes repeated false claims to have been a victim of modern slavery will also be removed to "crack down on those abusing the generosity of the British public and taking our country for a ride", she said.
The threshold for claims will be raised to make it harder for migrants to claim to be victims and delay their removal from the UK while their case is considered.
Under the new rules, migrants will be expected to provide objective evidence of modern slavery - such as medical reports on physical or psychological harm - toughening the current rules which allow claims on the basis of "suspicion" of abuse.
Mrs Braverman said: "It is totally unfair that genuine victims of modern slavery may be left waiting longer to receive the protections they need due to the flagrant abuse of the system.
"The changes will mean if you've committed an offence, we have the power to refuse your protections and kick you out of our country."
Previously, if a foreign national offender claimed to be a victim of modern slavery, any action to remove them would be paused while their claim was considered.
But from today, the Government will be able to prevent certain foreign criminals and anyone who has made false claims from accessing the protections provided by the National Referral Mechanism.
Under the changes, the Government will also be able to withdraw access to the initial and any wider protections such as a paused deportation if someone has been found to have made a "bad faith" claim to be a victim of modern slavery or human trafficking.
The Home Office said that could apply where there is enough evidence to conclude that an individual has falsely claimed to be a victim of modern slavery - for example, if a story about their journey to the UK does not match immigration records.
The measures are part of the Nationality and Borders Act and come ahead of a new illegal immigration bill that will bar any migrants who seek to enter the UK illegally from claiming asylum in the UK.
It was reported at the weekend that Government lawyers have raised concerns that detaining them for months - when the maximum permitted for terrorism suspects is 28 days - would ''never get through the courts''.