Hospitals have been warned only to offer placements to students from accredited medical schools.
The GMC says hospitals should act to ensure all staff are well-trained
The General Medical Council issued guidance after a BBC Five Live investigation raised concerns over private medical schools in the UK.
These schools, which charge thousands of pounds for training, claim degrees are awarded by overseas universities.
The GMC said it was unable to vouch for the quality of the training given by such schools.
The GMC, which held its council meeting today, said that there were 27 UK medical schools recognised for providing medical education which complied with the curriculum it had set out.
It added organisations offering clinical placements should ensure that students are studying at one of these schools.
But the GMC said it was aware that there were some private UK and non-UK based medical colleges offering medical courses.
It said that these colleges did not fall within the GMC's jurisdiction and were not supervised or quality-assured in any way by them.
In its factsheet, the GMC said: "Any organisation considering providing clinical placements for the students from such colleges should assure itself about the medical education provision and the quality assurance arrangements.
"The GMC is unable to provide a quality assurance role and organisations are therefore strongly recommended to undertake thorough investigations, and take appropriate advice, before providing clinical placements for such students."
Finlay Scott, chief executive of the GMC, said that by issuing this advice they wanted to help protect patients from poor quality care.
"We are saying to hospitals that, before you give anyone access to your patients, you must make sure that they are qualified to care for them."
After last month's BBC investigation, the GMC announced it had suspended its recognition of the degrees of one Luton-based college and was investigating the status of four others.
The watchdog said it wanted to check that named overseas universities actually did award degrees - and that the universities themselves were on a World Health Organization list of accredited institutions.
The investigation in being carried out in conjunction with the NHS Counter Fraud Service.