Ms Patel added: “These latest revelations are yet another reason to reject China’s sinister plan for a spy hub super embassy in the heart of our capital. The Conservatives are clear: Labour should put British interests first for once and throw out the embassy proposal.”

It comes after unredacted plans showing a network of underground chambers, including one just meters away from fibre-optic cables carrying critical data between the City of London and Canary Wharf, were exposed in a national newspaper.

The room is fitted with hot-air extraction systems, which the Telegraph reported suggested heat-generating equipment such as advanced spy computers could be placed in the rooms.

Shadow national security minister, Alicia Kearns demanded answers in Parliament after the staggering revelations came to light, warning the embassy would hand Beijing “a launchpad for economic warfare at the heart of the central nervous system of our critical national infrastructure”.

She demanded to know whether any minister had seen the unredacted plans before The Telegraph uncovered them, telling Housing Minister Matthew Pennycook: “Cables on which our economy is dependent. Cables carrying millions of British people’s emails and financial data, and access that would give the Chinese Communist Party a launchpad for economic warfare against our nation.”

Ms Kearns added: “The Home Office and the Foreign Office say security concerns have been addressed. So I put to the minister, had any minister seen these unredacted plans before the Telegraph uncovered them, and if not, why not?”

She warned that approving the embassy would “reward” China for holding British national Jimmy Lai in prison and demanded the Government come clean as to whether or not they knew about the web of secret rooms planned for the embassy.

Mr Pennycook insisted that the government had “not misled the House” but refused to comment on what he called “speculation” about secret rooms under the embassy.

He repeatedly refused to say whether any minister had seen the unredacted plans before they were exposed by The Telegraph.

Neither the Home Office, Foreign Office nor Housing Department has confirmed whether officials saw the complete plans before approving the application.

Luke de Pulford of IPAC said: “This mega embassy will unleash an unprecedented era of interference and intimidation upon the UK. The UK government has downplayed the risks posed by proximity to the cabling for over a year to MPs, journalists, and our closest security allies. It’s time they came clean and set out a comprehensive plan to mitigate these very real risks.”

Calum Miller, the Liberal Democrats Foriegn Affairs Spokesman said:

“The unredacted site plans for China’s proposed super embassy expose huge dangers- yet the Government still prefers to stick its head in the sand and is ready to wave through Beijing’s application.

“This super-embassy presents a grave threat to our national security. Less than a month ago, the government launched an urgent review of China’s financial interference in UK politics. The government should not take a decision before seeing the report.

“Greenlighting it would also send a shameful message to Hong Kongers in this country: that the Government is more interested in trade deals with China than protecting them from CCP intimidation.

“This weekend’s protest outside the Chinese embassy should be heard loud and clear by the Prime Minister. I challenge him to go and listen to the concerns of those Hong Kongers who fear the long arm of Beijing will only be strengthened by this embassy.”

Mr Pennycook insisted “all material considerations” including national security would be taken into account, but critics say the damage is already done.

But he faced a revolt from his own benches, with Labour MP Sarah Champion – who chairs the Commons International Development Committee – declaring: “I am in no doubt this mega-embassy should not be allowed to go ahead.”