Deputy prime minister Angela Rayner has demanded additional information from China over its plans for a new “mega” embassy in London after several of the drawings contained areas that were blacked out.

A letter sent by Rayner’s housing department to the Chinese embassy said it must provide unredacted drawings of the plans or “identify precisely and comprehensively” the parts that have been withheld, and “explain the rationale and justification” for the blacked-out sections.

The letter, sent on Wednesday and seen by the Financial Times, gives the embassy just two weeks to respond, saying a full decision by the government on China’s planning application for the site must be made by September 9. The late objection raises the prospect that ministers may reject the plans, which have been criticised by the White House.