Prime Minister Narendra Modi on Tuesday said opposition parties want a weak government at the centre to serve their vested interests and hide their corruption, adding that such a government cannot fight terror and end it."The opposition has been trying to form a weak government to serve their vested interest and to hide their corruption," Modi said while addressing an election rally in Muzaffarpur parliamentary constituency in Bihar.Modi said that the Bharatiya Janata Party(BJP)-led NDA will sweep the elections. "Four phases of polls have made it clear that opposition parties are losing, remaining three will determine the scale of their defeat."He said that the Opposition has no concern about national security and was afraid of speaking against terror.Modi also taunted the Opposition saying: "Many in 'Mahamilavati' gang may not win enough seats to help their bigwigs become leader of the opposition, but they are dreaming of Prime Minister's post."Modi, without naming the Rashtriya Janata Dal, said that if opposition parties regain strength, lawlessness will be back in Bihar.