SEOUL, Feb 16 (Reuters) -

The South Korean government warned on Friday that trainee doctors were putting public health at risk after more than 150 tendered their resignations to protest a government plan to admit more students to medical schools.

The health ministry said it had issued a back-to-work order to the 154 doctors at seven hospitals, warning that refusing to comply will result in punishment.

The government plans to raise medical school admissions by 2,000 students for the 2025 academic year and to add 10,000 doctors by 2035. Currently, about 3,000 students enter medical schools each year.

The plan has drawn intense protests from doctors and medical students, who say increasing the number of physicians would prompt unnecessary medical care and worsen the finances of the national health insurance plan.

Earlier, trainee doctors at the country's five biggest hospitals, all in Seoul, decided to resign effective Tuesday, the head of the Korea Interns and Residents Association (KIRA), Park Dan, said in a statement.

Media reports estimated the move would involve about 2,700 doctors, about a fifth of the country's medical interns and resident doctors. The system relies on them for emergency and acute healthcare.

The government said any collective action by doctors is illegal and it will respond firmly to strikes or refusals to work. It vowed to go ahead with the plan to increase doctors, which polls show have strong public support.

The health ministry has ordered all teaching hospitals to disregard resignations submitted by doctors and those who do not comply with the back-to-work order will be punished under medical services law, Vice Health Minister Park Min-soo said.

"There will be no amnesty or reprieve this time," Park told a news briefing.

A proposal by the government in 2020 to increase medical school admissions by 4,000 over 10 years was shelved after intense opposition from the medical community and a strike by trainee doctors.

At the time, the government pressed charges against 10 trainee doctors who went on strike but later dropped the charges and reinstated them.

The government plan aims to increase the number of doctors practising outside Seoul and in basic disciplines such as paediatrics and obstetrics, while expanding protection for the profession against malpractice suits and prosecution.

Doctors and medical students have said the plan will not address the overburdening of large teaching hospitals and a lack of incentives for doctors to practice in basic fields.

Doctors throughout the country held rallies on Thursday, calling on the government to scrap the plan. (Reporting by Jack Kim; Editing by Cynthia Osterman and Kim Coghill)