Campaigners have criticised a plan to demolish part of a Grade II listed building in Mayfair to create a public courtyard.
Under plans submitted to Westminster Council, an auction room to the rear of 20 Hanover Square would be demolished.
The Victorian Society said the structure was of "outstanding significance" and urged the council to reject the application.
The council said it cannot comment or it may prejudice the hearing.
Heloise Brown, conservation adviser for the Victorian Society, said: "20 Hanover Square is recognised as being of outstanding national significance and the auction room at the rear is an interesting and well-designed piece of architecture that reflects the changing use of the building.
"The developer has an obligation to provide public benefit from this scheme but this must not be fulfilled by destroying part of a Grade II listed building, particularly as there is already a large open space just metres away in Hanover Square."
The new public space is just one of the proposals put forward by developer, Great Portland Estates as part of the Crossrail project.
A station is to be built over the site of numbers 18 and 19 Hanover Square.
The developer could not be contacted for a comment.
John Walker, Westminster Council's operational director for development planning, said: "The application is currently being assessed and the comments of interested parties will be reported to the planning committee in due course.
"We cannot comment on the application further at this stage because it could prejudice the planning hearing itself."