Pakistan, Nigeria and Egypt top the list of nations with doctors and nurses working in the United Kingdom (U.K.) despite a ban on recruiting from those countries.
According to the British National Health Service (NHS) Code of Practice, Nigeria is among 97 nations that "should not be actively recruited from" because they receive aid or suffer from shortages of medical practioners.
However, figures revealed that one in four new NHS medics are from countries 'banned' from working for the health services sector.
A breakdown of the figures published by the Daily Mail UK showed Pakistan with the highest number of medics with 3,413, followed by Nigeria and Egypt with 1,995 and 1,775 medics.
Others are Sri Lanka with 826 medics, Sudan 797, Bangladesh 444, Iraq 326, Myanmar 312, South Africa 290, Nepal 166 and Jordan 160.
The figures showed the number of doctors joining the NHS from these countries have doubled in the past two years.
General Medical Council figures revealed that 4,161 doctors registered to work in Britain last year despite coming from countries that should not be recruited from.
This is a 1,955 increase from the 2,206 medics that migrated from the same countries in 2016 just as over 12,000 registrations took place from nationals of these regions in the past five years.
Also, 27 per cent of all new doctors working in the NHS are said to have emanated from 'banned' countries, compared to 13 per cent in 2014.
Chief Executive of the King's Fund, Richard Murray, expressed concerns that the NHS was too desperate to check if recruitment agencies were 'ethical' in their recruitment processes.
However, some of the individuals may have applied to work in the UK off their own backs rather than being actively recruited.
Concerns that 'banned countries' are being exploited emerged as NHS officials prepare to launch a global recruitment drive to fill vacancies.
He told The Telegraph UK: "The workforce shortages in the NHS mean it does need international recruitment but it needs to be done ethically. Increases in this scale from these countries are going to bring the UK into disrepute.
"I think organisations are so desperate to get professionals they just aren't checking whether it is done ethically."
According to the DailyMail UK, an ongoing recruitment crisis has struck all aspects of the NHS and reached unprecedented levels.
Experts, therefore, cautioned that frustrated medical practitioners are fleeing the health service in their droves due to funding issues, relentless pressure and even Brexit concerns.