Angela Rayner has given China two weeks to explain why parts of its plans for a new mega-embassy in London are redacted.
The deputy prime minister's Ministry of Housing, Communities and Local Government sent a letter asking for further information and requested a response by 20 August, the BBC understands.
Beijing's plans for the new embassy have sparked fears its location - very near London's financial district - could pose an espionage risk. Residents nearby also fear it would pose a security risk to them and attract large protests.
The BBC has contacted the Chinese embassy in London for comment.
A final planning decision on the controversial plans will be made by 9 September, the BBC understands.
