Angela Rayner has told China to explain why key parts of detailed plans for a vast new London embassy have been blacked out.

The deputy prime minister and housing secretary is demanding planning consultants for the Chinese embassy explain why detailed drawings for basement areas of the Royal Mint Court redevelopment plans have whole sections “greyed out”.

She has given Beijing until 20 August to respond as the Ministry of Housing, Communities and Local Government considers whether to grant planning for the called-in mega scheme.

The £255m scheme is set to be Europe’s largest embassy at 600,000 sq ft and is now being scrutinised by ministers after Tower Hamlets rejected the embassy plan over safety and security concerns in 2022.

The proposed super embassy would include offices, a large basement area, housing for 200 staff, and a new tunnel to connect embassy buildings

It would sit just east of the City of London, opposite the Tower, near sensitive fibre optic links used by banks and major institutions.

The project, designed by David Chipperfield Architects, would repurpose the listed Johnson Smirke and Seaman’s Registry buildings, demolish others to make way for new residences, and add offices, a basement, housing for 200 staff, and a tunnel between key embassy buildings.

Two buildings — the Cultural Exchange Building and Embassy House — have had internal layouts redacted, while other blocks are partly blanked out.

The Home Office has already called for a “hard perimeter” to block unregulated public access, a change that could trigger a new application.

Construction management advice is being provided by BCEGI UK, with Arcadis as project manager, Turner & Townsend as cost consultant, Arup on structures and civils, Cundall on building services, and Thornton Tomasetti on facades.

A final decision is due next month, but Rayner’s intervention leaves open the prospect that security concerns — not just planning policy — could derail what would be Europe’s largest embassy.