The UK's oldest medical union on Saturday hit out at government plans to increase the amount migrant workers pay to use the state healthcare service, to cover public-sector wage increases.
Prime Minister Rishi Sunak's government this week approved recommendations to boost wages of teachers, doctors and police by between 5.0 to 7.0 percent.
Sunak ruled out tax increases or government borrowing to fund the rise but instead said hikes in the Immigration Health Surcharge (IHS) and visa fees would raise £1 billion.
Doctors in Unite, which represents junior doctors, general practitioners and hospital consultants, said it was "appalled" at the move, as it would see migrants pay double to use the NHS.
Most employees in the UK have National Insurance contributions deducted at source on their salaries, which pays for the National Health Service, as well as state pension and unemployment schemes.
"Just like other workers, migrants contribute to NHS funding through general taxation. Doubling the NHS surcharge to over £1,200 ($1,570) per year is an unjust additional penalty," Doctors in Unite said.
"Migrants are effectively 'taxed twice' to access the same service," it added, calling the move "immoral and divisive".
The IHS, initially brought in to prevent "medical tourism", is now paid by most migrants under tighter post-Brexit entry rules.
It is paid per person in addition to visa fees for stays of more than six months.
Over-18s pay £624 per year while students and under-18s pay £470 per year.
The government has proposed raising the IHS for adults to £1,035, and £776 at the reduced rate.
Work and visit visas will go up by 15 percent, while the cost of student and leave-to-remain visas among others will rise by at least 20 percent.
Net migration in the UK hit a record 606,000 in 2022, according to official figures released in May, heaping pressure on the government, which has pledged to cut dependency on foreign labour.
Sunak has described legal immigration levels as "too high", and is separately battling record levels of asylum claims from migrants crossing the Channel in small boats.
Critics warn the IHS increases -- paid for by individuals or their companies -- could worsen under-staffing in many sectors, and prompt high-skilled workers and students to go elsewhere.
Migrant and refugee charity Praxis has accused ministers of treating people born outside the UK as "cash cows" at a time when they were struggling to repay already high visa renewal fees.
Genomics research centre The Wellcome Sanger Institute said it spent more than £300,000 in immigration fees for its employees in 2022.
"These proposed increases create further barriers for global talent... and will have a detrimental effect on UK and global science," said head of policy Sarion Bowers.