MUMBAI—India's central bank chief heightened his criticism of government spending, saying that without a credible plan to rein in debt, it will be hard to bring down inflation and accelerate the country's disappointing growth rate.

The comments by Duvvuri Subbarao, governor of the Reserve Bank of India, comes as India's leaders grapple with the toughest economic period in years. Through much of the past two decades, India had one of the fastest-growing economies in the world. But in the past year, persistent inflation, lofty...