Beijing’s application for the embassy was initially rejected by Tower Hamlets Council in 2022 over safety and security concerns.
However, it was taken over by the UK government housing department last year, after China resubmitted an application one month after Labour came to power.
Asked about the latest delay on Friday, Beijing’s ministry of foreign affairs accused the UK of “constantly complicating and politicizing the matter”.
Spokesman Lin Jian said the UK had “repeatedly put off the approval of the project citing various excuses and linked the project with other issues”.
“That goes entirely against the UK’s commitments and previous remarks about improving China-UK relations,” he added.
“We once again call on the UK to fulfil its obligation and honour its commitments at once, otherwise the consequences arising therefrom shall be borne by the UK side”.
Downing Street hit back at Mr Jian’s comments, saying: “We do not recognise any claims of assurances, and I can’t explain the statement they’ve set out.”
The PM’s official spokesman added: “Protecting the UK’s national security is our first duty.
“In terms of the planning process, as set out yesterday, this is a decision that is independent of the rest of government.”
He added it would not be “appropriate for me to comment further” on a decision being made by the housing department.