India's central bank was wrong to keep its benchmark interest rates unchanged on Thursday, according to veteran emerging markets investor Mark Mobius.

The Reserve Bank of India surprised markets by keeping its repo rate — the rate at which it lends to other banks — unchanged at 5.15%. Prior to the decision, economists predicted a sixth rate cut from the central bank amid a notable slowdown in the Indian economy.

"I think they did the wrong thing," Mobius, who is founding partner at Mobius Capital Partners, told CNBC's "Street Signs" on Friday about the RBI. "I think they were reacting to the short-term situation with inflation, which is mainly caused by food prices, and, specifically, onion prices."

In October, India's annual retail inflation rose to 4.62% on the back of higher food prices, Reuters reported. That was a tick above the RBI's medium-term target of 4%.

"They should have lowered rates," Mobius said, adding it could improve business confidence in the country and may help to solve some of the debt problems in India's financial services sector. He explained that the country is "going through a big adjustment right now because of the reforms that have taken place, particularly on the taxation side," referring to Prime Minister Narendra Modi's landmark Goods and Services Tax reforms.

The government has struggled to collect sufficient revenue since its new tax schemes went into effect in mid-2017. Recent reports said the GST structure is set to be reviewed.

"This is an adjustment that people have to be accustomed to and it takes time. But next year, I believe that this will do well — they would have made this adjustment and realize the reforms are having an impact," Mobius said, adding he remains bullish on India. Many micro, small and medium-sized businesses have struggled as a result of the new value-added taxes.