What do GlaxoSmithKline, Nestlé, Microsoft, Daimler and Qualcomm have in common? All are western companies under investigation by Chinese authorities for alleged wrongdoing. Foreign businesses believe they are being unfairly singled out.

Thirty years ago the Chinese government, desperate for foreign capital, enticed western companies with tax incentives and preferential land use policies. But the privileges on offer have gradually been abolished. The golden era for overseas investors has come to an end amid a flurry of bribery probes, antitrust investigations and allegations over food safety.

There is much speculation over the motives for these actions. Some believe the government is suppressing foreign competition to protect domestic industry. Others cite concerns over national security, given the proliferation of cyber espionage.