A Chinese official has called for a clampdown on the internet to stop spies using security holes to access sensitive information.

Lou Qinjian, vice minister of China's Information Industry, claims that the country's state and military secrets are being stolen by spies using the internet.

"The internet has become the main technological channel for external espionage activities against our core departments," Lou told the Chinese Cadres Tribune.

"In recent years party, government and military organs and national defence scientific research units have had many major cases of loss, theft and leakage of secrets, and the damage to national interests has been massive and shocking. "

Lou's statement may surprise many Western nations, which have recently accused China of hacking into their own government networks.

The US and Germany, along with the UK and France, have all accused Chinese hackers of invading their networks, although not all have pointed the finger directly at the Chinese government.

Lou's call to crack down on the internet also comes as researchers at the University of New Mexico and the University of California, Davis have questioned how strong the so-called Great Firewall of China really is.

The People's Republic of China stops the country's internet users from accessing content which it considers objectionable, but a study suggests that not all banned content is being blocked.

Researchers claim that China's censorship system is not a true firewall because some of the banned information passes through several routers in the country before being blocked.

A true firewall would block all mentions of a banned word or phrase in a message, but researchers found that banned words reached their destinations about 28 per cent of the time.

The study also found that the filtering system was particularly lax during times of heavy internet use.