NEW DELHI (Reuters) - India has ordered an investigation into doctors and laboratories suspected of offering kickbacks for referring patients for medical tests, following a sting operation by a TV news channel.

Hindi news channel News Nation TV showed laboratories in the national capital offering commissions as high as 50 percent to doctors who referred patients to their diagnostic centers.

The diagnostic market is the fastest growing segment of India’s $74 billion healthcare industry, according to consultancy PwC, with the segment forecast to grow to $17 billion by 2021 from $3.4 billion in 2011.

Newly appointed Health Minister Harsh Vardhan has vowed to clean up the health system, which he says is riddled with corruption, a problem that pervades public life in India.

India was ranked 94th in a list of 177 countries on Transparency International’s 2013 global corruption index, lower than China, South Africa and Brazil.

Officials at one laboratory visited by News Nation's undercover reporters said they had kickback arrangements with 10,000 doctors, with monthly payments running into tens of thousands of rupees for some neurosurgeons who prescribe expensive tests.(bit.ly/Ul7PBD)

“Nation shamed by sting operation on doctors taking commission for referring tests. Have ordered high level probe. Ethics need of the hour,” Vardhan wrote on his Twitter account late on Monday.

“Doctors should treat News Nation TV expose on commissions/kickback as a wake up call,” he wrote.

In the last few weeks, leading doctors and advocacy groups in India have teamed up to try to eradicate corruption from the industry, forming anti-graft panels at hospitals and writing open letters to Vardhan.[ID:nL3N0OK3DX]

“You can’t make a difference in one day,” said Balram Bhargava, a doctor who is forming a ‘Society for Less Investigative Medicine’ at the All India Institute of Medical Sciences. “It has to be a gradual process.”

The anti-corruption debate gained momentum in India after Australian doctor David Berger wrote a column in May describing his encounters with corruption at a charitable hospital in the Himalayas.