The UK has condemned Beijing after the US charged Chinese hackers accused of attempting to steal trade secrets and technologies in a bid to compromise government computers.
More than a dozen allies affected – including the UK – are expected to condemn China over allegations.
The US Justice Department revealed criminal charges against two hackers allegedly affiliated with Beijing's main intelligence service over a cyber-spying campaign targeting the US and others countries' networks.
According to reports, the charges accuse a group – known as APT 10 – of spying on some of the world's biggest firms by hacking into technology companies which managed email, storage and other computing tasks.
The countries affected are expected to accuse China of backing the large-scale operation, known as Cloudhopper.
They are expected to say it violates the terms of 2015 agreements to stop cyber espionage for commercial purposes.
A senior Whitehall source told Sky News it was "certain that UK and allies' trade secrets have been stolen" by APT 10.
The alleged hacking group, which is also known as Stone Panda and Menupass, is a Tianjin based group which has been operational since 2009, according to Sky sources.
Its members are not conventional state employees, but condoned and working in concert with Chinese of state security, the source told Sky News.
"They are more like a corporation than a gang," the senior Whitehall source added.
"The tentacles of this campaign are vast. It involves very widespread targeting of globally significant companies, including 'household names' – and this campaign is still ongoing."
Foreign Secretary Jeremy Hunt said the hacking campaign was "one of the most significant and widespread cyber intrusions against the UK and allies uncovered to date".
"These activities must stop," he said in statement. "They go against the commitments made to the UK in 2015, and, as part of the G20, not to conduct or support cyber-enabled theft of intellectual property or trade secrets.
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"Our message to governments prepared to enable these activities is clear: together with our allies, we will expose your actions and take other necessary steps to ensure the rule of law is upheld."