Spies would monitor the computer systems of a Chinese-backed new Sizewell power station if asked by the Government, it has emerged.

Security agency GCHQ confirmed it would help with cyber security at nuclear power stations, if asked, amid concerns that Chinese involvement could threaten national security.

The revelation came ahead of the state visit by the Chinese president Xi Jinping, which is expected to see plans to build three nuclear power stations, including a replacement hub on the Suffolk coast, move a step closer.

An announcement that the Chinese will invest in the new power stations is anticipated amid a lavish state visit this week.

China is expected to join energy giant EDF in backing Hinkley point and Sizewell C, and could also be given the opportunity to design and build its own nuclear power station at Bradwell in Essex.

It emerged last week that security chiefs had voiced concerns about the landmark deal because of China’s perceived threat to the UK over cyber spying.

They have reportedly warned that ‘trapdoors’ could be installed in software used to run the nuclear power plants which could enable Beijing to seize control of them if diplomatic relationships were to break down.

Questioned about the security implications of the deal with China by Labour MP Paul Flynn, foreign office minister Hugo Swire said security in the civil nuclear industry was of paramount importance to the Government.

“The UK has in place, robust security regulations which are enforced by an independent regulator, the Office for Nuclear Regulation. These regulations cover sensitive nuclear information as well as holdings of nuclear material and nuclear sites. The Government keeps the regulatory framework for security in the civil nuclear industry under continuous review.”

Suffolk Coastal MP Therese Coffey said: “The Office for Nuclear Regulation is one of the toughest regulators in the world. While some people may be initially concerned, Chinese investment in nuclear power in the UK doesn’t change the rigorous regulation regime.”

A GCHQ spokesman said: “GCHQ has a remit to support the cyber security of private sector owned critical national infrastructure projects, including in the civil nuclear sector and nuclear new builds, when invited to do so by the lead government department involved.”