Meanwhile, according to the outlet, analysis of land registry documents has revealed that China has built up a portfolio of 50 properties in Britain, most of which don’t have official status, and some have no official use.

The newspaper says cars with number plates indicating official diplomatic vehicles are often parked outside, and cited sources saying diplomats and their families live in some of them.

The Times reports that these properties are effectively covered by the same “inviolability” as the country’s embassy and other diplomatic buildings under article 30 of the Vienna Convention on Diplomatic Relations.

China’s property portfolio in London is estimated to be worth £100million, excluding the new embassy site, and includes a five-storey brick mansion in Hampstead which once operated as the cultural section of the embassy but is no longer featured on an official list, according to their investigation.

It also has a two-storey detached house close to China’s official science and technology section in St John’s Wood, which has no official use, the outlet reports.

Among its other assets is an apartment block that’s home to the London office of Xinhua, the state news agency often accused of spreading misinformation.

Approached by The Times, the Chinese embassy initially disputed that it owned these properties and didn’t reveal what the properties are, what they’re used for, or whether China will retain them if the embassy is built.

A spokesperson said: “Our planning application for the new Chinese embassy project has fully complied with international diplomatic practice and the UK’s local planning policy. All required procedures have been completed.

“The repeated postponement of the decision on our planning application is unjustified. We urge the UK side to approve our application quickly and without further delay, to avoid further undermining the mutual trust and co-operation between the two sides.”

“The claim that ‘Chinese embassy staff are spies’ is purely fabricated and absurd,” he said, adding that it is “not even worth responding to”.

China insists its efforts to massively upsize its embassy, moving from its current site in Marylebone, will “promote understanding and friendship” and help develop “mutually beneficial cooperation”. The UK Government has delayed a decision on whether to greenlight the new embassy on a number of occasions, but reports suggest ministers could give it the go-ahead in January following months of internal wrangling.

There is particular concern about a series of underground cables nearby linking the City to Westminster. However, the Home Office and Foreign Office, which represent MI5 and MI6, will not be raising any formal objections to the plans.

Sir Keir has been under intense pressure to block the plans after a series of alleged spy plots were discovered linked to Beijing, including a case against two suspected moles, Christopher Cash and Christopher Berry, which collapsed earlier this year. Both men have denied any wrongdoing.

A Government spokesperson previously said: “An independent planning decision will be made by the secretary of state for housing, communities and local government in due course.”

“The Home Office and Foreign Office provided views on particular security implications of this build in January and have been clear throughout that a decision should not be taken until we had confirmed that those considerations had been completed or resolved, which we have now done.

“Should the planning decision for a new embassy in the London borough of Tower Hamlets be approved, the new embassy will replace seven different sites which currently comprise China’s diplomatic footprint in London which clearly brings security advantages.”