Culture secretary Chris Smith has ordered an investigation into the restoration of the Great Court at the British Museum, focusing on “apparent misrepresentation”.

The row over the use of French limestone rather than English Portland stone for the portico reached new heights this week when English Heritage condemned part of the restoration work and ordered it to be taken down and replaced.

In letter leaked to Building dated 6 October, Smith told MP Ian Bruce, who has raised the issue with the department, that he was concerned by the issues raised.

Smith said the British Museum had concluded that the French limestone was similar to Portland and therefore within the terms of the contract. But he added: “We are, however, concerned at the apparent misrepresentation to the British Museum that Portland Stone was being supplied.”

The British Museum received £1.9m in lottery funding for the restoration of the portico on the understanding that it used Portland or a suitable substitute that matched the existing stonework.

We are concerned at the apparent misrepresentation to the museum that Portland stone was being supplied

Chris Smith, Culture Secretary

An inquiry by English Heritage concluded that French limestone was an adequate substitute, but added that the work failed to meet the specifications set out in the listed building consent.

Easton Masonry, the company that supplied the stone, refused to comment. The Department for Culture, Media and Sport also refused to be drawn on the subject, but confirmed that an investigation was taking place. Said one spokesperson: “There have been so many allegations that our officials need to establish the facts of the case.”

A spokesperson for the British Museum said: “We will pay the correct value for the stone that has been provided.”