The Health Professions' Council of South Africa has launched an investigation to verify the qualifications of more than 4500 medical professionals working in government hospitals.

The joint operation by the medical regulatory body, the Department of Health and the police, is believed to be one of the biggest audits ever undertaken in the medical profession.

An inquiry by the council last year uncovered that 1053 personnel, from paramedics to ambulance basic assistants, had fraudulent qualifications. The practitioners have since been deregistered by the council.

The latest investigation - going back 10 years - will focus on finding foreign practitioners who are practising with fraudulent or unverifiable qualifications. According to its database, 1359 foreign medical professionals registered between 2007 and December. The council this week described the probe as a "daunting but necessary task".

"There are thousands of files that need to be audited," said Dr Kgosi Letlape, acting registrar and chief executive. "It is difficult to say [how many illegals are practising in the country]."

The nationwide crackdown was triggered by the arrest of a Congolese doctor who worked as a neurosurgeon for about four years at several government facilities before the council discovered his fake credentials and deregistered him in December. Dr Nyunyi Wambuyi Katumba worked at the Steve Biko Academic Hospital and Mediclinic Medforum in Pretoria and Chris Hani Baragwanath Academic Hospital in Joburg.

The Health Department warned that council employees who assisted in illegally registering foreign practitioners would also come under scrutiny . Police spokesman Brigadier Lindela Mashigo said illegal practitioners would be charged.