Heritage Lottery Fund threatens to order demolition of portico in Great Court because of Portland stone row.
A Portico at the British Museum may be demolished at a cost of £1m because it has been restored using the wrong stone.
The Heritage Lottery Fund has suspended funding for the restoration of the south portico in the Great Court of the museum, in central London, after discovering that French limestone had been used instead of the more expensive British Portland stone, which matches the courtyard's existing fabric.
A spokesperson said the fund was waiting for the result of an investigation into the quality of the stone before making a decision about withdrawing funding completely.
The lottery grant represents 89% of the south portico's restoration cost of almost £2m. The museum's original bid for lottery money was based on the installation of stone that matched the original in the courtyard but this was considerably more expensive than other types of limestone.
A spokesperson for English Heritage said that the work, completed by Easton Masonry, contravened listed building consent, and the restored portico could be demolished.
The spokesperson said: "We have the powers, and, if it is felt to be appropriate, we will use them."
If the existing work is demolished and the south portico rebuilt, the final cost would soar to more than £3m and delay the opening by at least four months, said English Heritage.
A leaked briefing document written by English Heritage and two reports commissioned by scheme architect Foster and Partners and the heritage fund say the stone will not mature in the same way as Portland stone.
The briefing document said Easton had been instructed to replace a series of architrave stones in the portico's three entrance portals with Portland. The company has also been told to replace other areas of the stonework that have been incorrectly bedded and built with additional joints without the prior knowledge of the architect.
A spokesperson for the British Museum said: "We are using over 900 tonnes of Portland. But with the project's timetable, the contractor couldn't get the particular size and quality from Portland. We hope to convince English Heritage that the stone supplied is adequate. We hope it won't come to demolition."
Easton Masonry was unavailable for comment.
“We hope to convince English Heritage … and hope it won’t come to demolition ”
Spokesperson, British Museum