Nepal's second largest party CPN- UML has refused to join the government due to dispute over the ministerial portfolios with first largest party Nepali Congress ( NC). NC President Sushil Koirala was elected country's prime minister on Monday and UML had strongly backed the government. Koirala, who take oath of office and secrecy from president on Tuesday afternoon, failed to bring the UML ministers in the government. UML leaders said that Prime Minister Koirala refused to grant them Ministry of Home Affairs as per the bilateral agreement between two parties before the prime ministerial election. NC and UML had signed seven-point deal on Sunday which led to the formation of Koirala-led government and two parties agreed to form a coalition government. Home Ministry is regarded as a powerful ministry in Nepal which has a direct control over key security agencies of Nepal -- Nepal Police, Armed Police Force and National Investigation Police. This ministry always becomes the bone of contention among the parties at the time of government formation in Nepal. "We will not join the government until and unless the agreement reached between two parties is implemented," UML Secretary Bishnu Poudel told reporters after the meeting. UML's decision not to join the government is a serious blow to Koirala. Leaders from both side said they would try to settle the dispute through consensus and dialogue. After the key coalition partner refused to join the government, Koirala formed two-member cabinet on Tuesday after taking the oath from the head of the state. Koirala has named Ram Sharan Mahat as a minister in his cabinet without giving him any portfolios. Meanwhile, Koirala has assumed the office on Tuesday afternoon after taking the oath. After taking office, Koirala reiterated his commitment to delivering a new constitution within a year. He said that maintaining law and order in the country and controlling the corruption are the main priorities of the government.