UK Home Secretary Priti Patel has set out plans for a "fair but firm" overhaul of the immigration system that will make it harder for some asylum seekers to stay permanently in the country.
Under the new plans, only migrants who arrive in the UK through official channels, such as refugee schemes in war zones or escaping persecution, will be entitled to stay permanently.
Others will be eligible for "temporary protection status" under which they will be reassessed for removal at a future date.
Proposals include bringing in a new body to determine the true age of applicants over concerns that some adults are posing as children.
The government will also curtail the ability of migrants to claim "family reunification" rights to bring their relatives to the UK.
Setting out the plans in the House of Commons, Ms Patel said the new system would be "faster and fairer" and would help stop people smugglers.
"If you illegally enter the UK via a safe country in which you could have claimed asylum, you are not seeking refuge from imminent peril, as is the intended purpose of the asylum system, but are picking the UK as a preferred destination over others," she told MPs.
Earlier, Ms Patel said the government would introduce the new system because currently the UK was "unable to fully help people who are fleeting persecution" due to "the extent of illegal migration taking place".
She said the proposed system rewarded those who came through legal routes, such as the United Nations Refugee Agency, and discouraged those travelling via safe countries such as France, where thousands of migrants use small boats to make the dangerous crossing across the English Chanel.
More than 100 migrants, including a young girl, crossed the Channel on Tuesday, adding to the 806 migrants who have arrived on small boats this year.
Efforts will be stepped up to remove Channel-crossing migrants who could have claimed asylum in safe countries from which they travelled, such as France.
Britain's main opposition Labour Party said the government lacked "competence and compassion", while refugee advocates branded the changes "inhumane".
The Home Office said its review would focus on three areas: increasing fairness and efficiency; deterring illegal entry; and easing the path for deportations.
Ms Patel said the UK would create "safe and legal routes" for asylum seekers to come to the UK.
"It's important to recognise that we are unable as a country right now to fully help people who are fleeing persecution and who are destitute in the world because of the extent of illegal migration that is taking place, where people are putting their lives at risk and fuelling criminality," she told BBC's Radio 4 Today programme.
"We will bring in changes of the system where we effectively create safe and legal routes."
She said people were dying "in the hands of gangsters and people smugglers" on their way to Britain.
"We cannot carry on as we are," she said.
But refugee groups said the proposed changes would create a "two-tier system" where cases are not assessed on their merit.
Enver Solomon, chief executive of the Refugee Council, said the government's plans could undermine the country's traditions of providing protection for people “regardless of how they have managed to find their way to our shores”.
"[The government] is seeking to unjustly differentiate between the deserving and undeserving refugee by choosing to provide protection for those fleeing war and terror based on how they travel to the UK,” he said.
Mike Adamson, chief executive of the British Red Cross, said the changes were “inhumane”.
"We should not judge how worthy someone is of asylum by how they arrived here," he said.
“The proposals effectively create an unfair two-tiered system, whereby someone’s case and the support they receive is judged on how they entered the country and not on their need for protection."
As part of the Brexit debate, campaigners said the country needed to update the system after its EU exit, as immigration was one of the key reasons why many people voted to leave the bloc in the 2016 referendum.
Ms Patel said her New Plan for Immigration would stop some asylum seekers receiving the same entitlements as others.
“If, like over 60 per cent of illegal arrivals, they have travelled through a safe country like France to get here, they will not have immediate entry into the asylum system, which is what happens today," she said.
“And we will stop the most unscrupulous abusing the system by posing as children by introducing tougher, more accurate age assessments."
Ms Patel announced a policy to deter human traffickers.
“Profiteering from illegal migration to Britain will no longer be worth the risk, with new maximum life sentences for people smugglers.
"I make no apology for these actions being firm, but as they will also save lives and target people smugglers they are also undeniably fair."
The immigration overhaul, which will be formally introduced in the UK Parliament on Wednesday, featured in a speech she made in October 2020 at the Conservative Party's annual conference.
Then, Ms Patel, whose parents of Indian descent emigrated from Uganda to Britain in the 1960s, said the new rules would welcome people through “safe and legal routes”.
Enver Solomon, chief executive of the Refugee Council, said the proposal went against traditional British values.
“This is wholly unjust and undermines the UK’s long tradition of providing protection for people, regardless of how they managed to find their way to our shores," he said.
Bridget Chapman, of the Kent Refugee Action Network charity, which works in one of the coastal areas where many refugees arrive on British soil, was distressed by the new plan.
"There are people who have been displaced, through no fault of their own, who've ended up coming to Europe and they're still in need of a safe place," she said.
"They are not going to stop coming. We have to find a different, more humanitarian way to deal with those who are going to come."
A record 8,400 asylum seekers tried to cross the English Channel last year.
Since January, the government has been trying to pass laws that give British border police more powers to obtain fingerprints from migrants trying to cross the Channel.