Mangala Samaraweera, finance minister in Wickremesinghe's sacked cabinet, said Saturday that their United National Party (UNP) would file a challenge with Sri Lanka's top court next week, saying the president had "kicked the constitution in the teeth".
The dissolution, which is expected to be challenged in court, was revealed in an official gazette notification signed by Sirisena which also set the next sitting of parliament for January 17.
Sri Lanka will hold a snap election in January, the country's president announced late November 9, hours after dissolving parliament when it became clear his prime minister nominee did not have a majority.
"At the moment we have 104 or 105 MPs", UPFA spokesman Keheliya Rambukwella told reporters, adding that the Sirisena-Rajapaksa group hoped to secure support from "crossover" legislators.
Supporters of ousted Sri Lanka's Prime Minister Ranil Wickremesinghe shout slogans as they gather at the prime minister's official residence in Colombo. Previously, Sirisena's party admitted to not having the votes to confirm ex-strongman Mahinda Rajapaksa as the new prime minister. "Maithripala Sirisena dissolved a parliament where we enjoyed a majority", he said.
Sri Lanka's largest party announced Saturday a legal challenge to President Maithripala Sirisena's sacking of parliament, a move that has plunged the Indian Ocean island nation into fresh turmoil and alarmed the worldwide community. But the admission of a lack of a majority had fuelled speculation that he might sack the legislature and go for a snap election.
Sirisena suspended Parliament for two weeks in a move Wickremesinghe's backers said was created to buy time to shore up support. At least eight have switched sides, but at least 120 deputies in the 225-seat parliament remain loyal to Wickramasinghe.
The leftist People's Liberation Front (JVP), which regards the sacking of Wickremesinghe as unconstitutional, accused Sirisena of trying to consolidate his power grab.
Wickremesinghe, who has not left the Temple Trees residence since his sacking, maintains that the action against him was unconstitutional and illegal, and insists his group can muster a majority.
Independent legal experts had told Reuters that parliament could be dissolved only in early 2020, which would be four-and-half-years from the first sitting of the current parliament. However, on November 1, he lifted the suspension after coming under severe criticism.
The EU said Friday, before the dissolution, that the crisis had scarred the Indian Ocean island's global reputation.
The U.S. State Department tweeted that it is deeply concerned by news the Sri Lanka Parliament will be dissolved, "further deepening the political crisis".
"You have not let this country be plunged into the darkness of dictatorship".