NEW DELHI — India’s Supreme Court on Wednesday faulted the country’s archaeological conservation body for failing to protect the Taj Mahal from discoloration, dirty feet and green slime emitted by millions of mosquito-like insects.

Since 2015, the body, the Archaeological Survey of India, has overseen a restoration project at the Taj Mahal, with workers scaling scaffolding to remove grime from the 17th-century tomb, which was built by the Muslim emperor Shah Jahan for his favorite wife, Mumtaz Mahal.

But last week, the Supreme Court called in officials of the organization to respond to criticism that work was taking too long. Over the years, as millions of tourists have flocked to the Taj Mahal in northern India, the monument’s appearance has deteriorated, its pearly white facade growing dull and the dirt from barefoot visitors blackening the grounds.

During Wednesday’s hearing, a lawyer for the Archaeological Survey of India, A.D.N. Rao, said that algae was a big source of the discoloration, despite a report from the survey attributing the problem to millions of insects that excrete a green substance on the Taj Mahal’s walls during mating flights. Experts have previously said the algae in the nearby polluted Yamuna River had led to an increase in the number of insects.