The department said: “A decision will be taken today on when entry to the queue for Her Majesty The Queen’s Lying-in-State will close as it reaches final capacity.
“Queue times are already 13.5 hours and may increase. To avoid disappointment please do not set off to join the queue.”
The waiting time had increased to 14 hours by 10am, with queues extending from Westminster Hall to Tate Britain.
An alternative, accessible queue for disabled mourners had already closed on Saturday, September 17 when all timed slots were filled.