Net migration in the UK hit a record 606,000 in 2022, official figures showed on Thursday, heaping pressure on the government, which has pledged to cut dependency on foreign labour.
Responding to the figures, Prime Minister Rishi Sunak described legal immigration levels as "too high".
"It's as simple as that and I want to bring them down," he told ITV in an interview.
Measures announced earlier this week to tighten the number of international students allowed to bring their families with them would have a significant impact, he added.
Immigration has long been a key political issue in the UK and was one of the main battlegrounds of the Brexit referendum in 2016, which saw the country leave the European Union.
In 2021, net migration -- the difference between the number of people leaving the UK and those arriving -- was 488,000.
Jay Lindop, director of the centre for international migration at the Office for National Statistics (ONS), said world events such as the end of the Covid-19 pandemic and Russia's invasion of Ukraine played a part in the increase.
China's squeeze on civil rights in Hong Kong, which led to the UK relaxing entry rules for holders of British overseas passports, also had an impact.
"A series of unprecedented world events throughout 2022 and the lifting of restrictions following the coronavirus pandemic led to record levels of international immigration to the UK," said Lindop.
Brexit brought an end to the policy of free movement of people from EU member states, which many businesses have since blamed for a shortage of workers.
Among those hardest hit have been agriculture, and the health and social care sector, prompting the government to relax immigration rules to try to plug the gap.
The main opposition Labour party's home affairs spokeswoman, Yvette Cooper, called the latest figures "extraordinary" and said it showed the government had "no plan and no grip" on the issue.
"Ministers have completely failed to tackle skills shortages or help people back into work after Covid," she added.
Sunak is under pressure from within his own Conservative ranks to restrict immigration, with right-wingers arguing that the current numbers are unsustainable.
Adding to his woes is a growing backlog in the Home Office's processing of asylum claims, particularly of migrants crossing the Channel from northern Europe in small boats.
Attempts to send failed asylum seekers to Rwanda, prompted by an unprecedented 45,000 arrivals last year, have been stuck in the courts.
So far, no one who has had their asylum application turned down has been sent to the central African nation as part of a deal between London and Kigali.
Separate figures also released on Thursday showed that the number of outstanding asylum claims at the end of March 2023 stood at just over 172,000 -- up 57 per cent from some 109,000 the previous year.
Of the 172,000 waiting for an initial decision, nearly 129,000 were waiting for more than six months -- a 76 per cent increase the same period to March 2022.
Sunak said he believed the measures his government was taking to lower legal migration would "bring the numbers down over time".
But he said he believed it was the issue of failed asylum-seekers that was of greatest concern to UK voters. A general election is expected next year.
Measures such as tightening the rules on overseas students went "alongside our other plan... to stop the boats because that's really important", he added.
Sunak argued that housing asylum-seekers in hotels while their applications are processed was costing large sums of taxpayers' money and diverted resources from others.
"How can it be fair for someone to come here illegally when there are people who are waiting their turn and doing it properly?" he said.
"There are lots of vulnerable people in the world that we want to welcome here and look after. We can't do that while the system is full of people who jumped the queue."
But critics said the backlog was an issue of the government's own making, while its policy of restricting legal migration through safe routes would only exacerbate the "small boats" problem.
"Leaving people in limbo like this, unable to work, separated from family and uncertain about their future, is costly to people's physical and mental health and the taxpayer," said Christina Marriott, from the British Red Cross.
"Processing claims more quickly would help people settle into communities, start work and get on with their lives."