Jharkhand's National Democratic Alliance minister Kamlesh Singh has decided to quit the Arjun Munda ministry after the police allegedly detained him.
Three independent ministers have already deserted the Bharatiya Janata Party-led government.
"The chief minister does not have confidence in his own ministers and it is unacceptable to continue in the Cabinet," Singh, who was the water resources, food and civil supplies minister, said.
"I am sending the resignation letter to both the governor and the chief minister later in the day," he said.
Singh said he took strong exception to the police intercepting his vehicle while he was heading to Kolkata to catch a flight to Delhi to meet the three dissident ministers - Madhu Koda, Enos Ekka and Harinarain Rai.
"A group of policemen surrounded my car in Jamshedpur, searched the vehicle and then they seized the keys from my driver, saying that they were carrying out the orders at the behest of the chief minister," he said. Accusing the chief minister of insulting his "own Cabinet minister", Singh said he had decided to meet the three ministers in Delhi as his repeated pleas for a rapprochement with them failed to yield results.
All the three ministers are reportedly in touch with opposition United Progressive leaders.
Singh, who is the lone minister from the Nationalist Congress Party, said it was too early to comment on whether he would go with the UPA in the event of a power-shift.
The 18-month-old NDA government in Jharkhand has a wafer-thin majority and would face a crisis in the event of the three ministers withdrawing support.