China leads the list of countries hacking into government computers that contain Britain’s military and foreign policy secrets, Whitehall sources said yesterday.

The emergence of Beijing as one of the most hostile state hackers has been highlighted in the United States this week, with allegations that the Chinese People’s Liberation Army tried to extract secrets from a computer in the Pentagon office of Robert Gates, the US Defence Secretary.

President Bush suggested that he intended to confront China directly over the claims that it has been trying to hack into Pentagon and other US government computers. Mr Bush hinted that he was prepared to risk a diplomatic rift by raising the sensitive issue with President Hu Jintao when the pair meet in Sydney today at the Asia-Pacific Economic Cooperation (Apec) summit.

One Whitehall source said that China was switching increasingly from “old-fashioned espionage” techniques to electronic hacking. The source said: “China is engaged in hostile intelligence activities, and instead of using the old-fashioned methods [recruiting agents and stealing blueprints], they are focusing on electronic means to hack into systems to discover Britain’s defence and foreign policy secrets, and they are technologically pretty advanced and adept at it.”

China v the West: an ongoing digital struggle

High-tech espionage is widespread and sophisticated – and that's just the attacks we know about

• Beijing denies launching cyberspace attack

• Estonia accuses Russia of ' waging cyber war'

Related Links

• China v the West: an ongoing digital struggle

• Beijing denies cyberspace attack

Another official said that the first warning about state-sponsored hacking was circulated around Whitehall two years ago. “China was not named but the hacking was believed to have come from there,” the official said.

MI5 has told the Government that at least 20 foreign intelligence services were operating to some degree against British interests, and that China and Russia were of greatest concern.

Advice on how to counter the Chinese hackers is provided by the Centre for the Protection of the National In-frastructure (CPNI), which is answerable to Jonathan Evans, the director-general of MI5.

All Ministry of Defence and Foreign and Commonwealth Office computers that contain sensitive material have special firewalls and antivirus software. However, CPNI has cautioned Whitehall that the rapid growth of wireless technology has raised the threat posed by hackers. “A key implication of this unprecedented wireless connectivity is that attackers can reach you at all times,” the CPNI says on its website.

In Sydney, Mr Bush said that he was aware that “a lot of our systems are vulnerable to cyber attack from a variety of places”. He said: “In terms of whether or not I’ll bring this up to countries . . . from which there may have been an attack, I may.” He then went on to talk about America’s “complex relationship” with China.

This week Beijing denied launching cyber attacks against the Pentagon. The Chinese Foreign Ministry said that there had been “wild allegations” against China, reflecting a “Cold War mentality”.

Times Recommends

• Times Charity Appeal: SolarAid
• Is it Black Monday all over again for Dubai?
• Behind the scenes at the biggest deal