"There is no harm if the country benefits from it," Congress spokesperson Renuka Chowdhury told reporters.
She defended the ASI move to excavate for around 1,000 tonnes of gold, which a seer said he dreamt to have been buried near a temple at the old fort.
"The Geological Survey of India said there is some metal underneath the temple. What actually is there will be known only after digging," said Chowdhary.
The old fort at Dondia Khera village belongs to Unnao's mid-19th century ruler Raja Rao Ram Bux Singh.
Unnao is 50 km from the state capital Lucknow.
Shobhan Sarkar, a famous seer of the region, wrote to the prime minister that the late king came in his dreams and asked him to get the treasure dug up and hand it over to the government of India to tide over the economic crisis.