MUMBAI, India — India’s top central banker resigned on Monday after tussling for months with Prime Minister Narendra Modi’s government over its desire to exert more control over the bank’s regulations and tap its reserves to increase government spending.

The departure of the banker, Urjit Patel, came almost a year before his term was to end and sent India’s currency, the rupee, down nearly 2 percent. Concerns about a slowing economy and a sharp spike in oil prices had already caused India’s stock market to give up most of its gains for the year.

“This will give a very bad signal to the Indian markets,” said Sebastian Morris, a professor of economics at the Indian Institute of Management in Ahmedabad. “It establishes beyond a doubt that Mr. Modi cannot get along with anyone with an independent mind.”

Officially, Mr. Patel said he was resigning for “personal reasons.” And Mr. Modi posted a message of praise for the economist on Twitter, saying, “Dr. Urjit Patel is a thorough professional with impeccable integrity.”