Lottery fund and English Heritage waiting for report from consultant before making south portico decision.

The French stone used in the new south portico of the British Museum may be stained to make it match the British Portland of the original.

  An investigation into the decision to use the cheaper imported limestone was ordered last year and its report is due to be released next month. Now a source close to the scheme says it has been decided to stain the French stone to try to make it blend in with the existing Portland stone in the museum’s Great Court. The portico is part of the £57m restoration of the British Museum.

The source said: “The moment they took the scaffolding down the difference in colour was obvious. It looks like they have painted the portico in magnolia paint. That’s why they are reduced to having to paint it with a darker stain.”

English Heritage considered demolishing the Foster-designed portico when it was revealed that Portland had not been used but eventually agreed to continue the work with French stone.

Foster and Partners declined to comment on the portico’s stone. An English Heritage spokesperson said it was aware of the portico’s appearance, but insisted that no decision would be taken on staining it until site work was completed.

The spokesperson said: “It is an issue we will need to consider but we cannot take any decisions until the work is completed to the architect’s satisfaction. You have to take account of the fact that this is a new building in a historic context. Some of the restoration work done elsewhere in the Great Court also shows variation in colour. You have to accept a certain difference in tone.”

The Heritage Lottery Fund suspended funding after the use of the French stone had been revealed. It is providing 89% of the £2m for the portico’s restoration. A Heritage Lottery Fund spokesman said a decision on funding would be taken after consultation with English Heritage and the release of a PricewaterhouseCooper report into the management of the stone contract. This is due to be published in six weeks.

English Heritage is also set to decide what work needs to be carried out on the jointing on the portico’s ashlar wall, frieze and flat pediment, after describing previous work as unacceptable.

Both the colour and jointing of the stone may affect the portico’s status as a listed building. If the work is found to have contravened the listing rules enforcement action can be taken by the local planning authority.