China's plans for a new embassy on the site of a two-century-old building near the Tower of London have stalled for the past three years because of opposition from local residents, MPs and Hong Kong pro-democracy campaigners in Britain.
Concerns that the new embassy could be used as a base for spying have prompted some politicians in Britain and the United States to urge the government to block Beijing's plans.
In a letter seen by Reuters, the Department of Housing said it would now rule by January 20 whether the project could go ahead, rather than December 10, because of delays in responses from the interior and foreign ministries.
A spokesperson for Prime Minister Keir Starmer said the delay was because those ministries had provided views on "particular" security implications of approving the embassy and a decision should not be taken until they had been considered.
China's embassy in London said it deplored the latest delay.
"We strongly urge the UK side to approve our planning application quickly to avoid further undermining mutual trust and cooperation between the two sides," a spokesperson said on Wednesday.
Luke de Pulford, executive director of the Inter-Parliamentary Alliance on China and a long-standing critic of plans for the embassy, said the latest delay was "entirely of the government's own making".
"Rather than this endless deferral, which will only make Beijing more angry, the government should say no, and get it over with," he told Reuters.
The timing of the decision is politically sensitive for Starmer's government after officials were recently accused of playing down the threat China poses to Britain's national security by allowing the collapse of a trial of two British men charged with spying for China.
Starmer warned on Monday that China poses "national security threats" to Britain, but added closer business ties are in the national interest.
The Chinese government purchased the site for the new embassy, at Royal Mint Court, in 2018 but its requests for planning permission were rejected by the local council.Â
Chinese President Xi Jinping asked Starmer last year to intervene.
Opposition politicians have called on the government to block the plans because of the proximity to strategic fibre-optic cables that go underneath the site.