The Court of Appeal has issued an interim order halting Mahinda Rajapaksa, his ministers, deputy ministers, and state ministers from continuing to function in their respective portfolios.
Rajapaksa said he will take his appeal to the Supreme Court on Tuesday and seek an order halting the decision.
As many as 122 parliamentarians of Wickeremesinghe's United National Party, Janatha Vimukthi Peramuna (JVP) and Tamil National Alliance last month filed a petition in the Court of Appeal challenging Rajapaksa's authority as the prime minister.
UNP leader Ranil Wickremesinghe says that if a General Election is necessary, a legal government should be established and a motion should be brought in the Parliament.
"There is a possibility of withdrawing the gazette", said a source in regular discussion with Sirisena, referring to the official announcement by which the president dissolved parliament.
According to leading lawyer, J.C.Weliamuna, the President of Sri Lanka Maithripala Sirisena must now appoint a new Prime Minister and a new Council of Ministers.More news: IDF Operation Located Terror Tunnel Outside Metula
But Rajapaksa has failed to show a working majority in parliament and lost two no-confidence votes.
Sirisena, a former opponent of Rajapakse, told a group of legislators on Monday that he would not reinstate Wickremesinghe even if the latter had the support of all 225 members of the legislature.
The court order also came as Mr Rajapaksa was set to present an interim budget for the first few months of 2019.
Sri Lanka's toppled premier likened the president to Hitler on Tuesday as he demanded to be reinstated, nearly six weeks into a paralysing political crisis in the Indian Ocean nation.
File image of former Sri Lankan president Mahinda Rajapaksa. The Supreme Court overturned Mr. Sirisena's decision to dissolve Parliament and halted the preparations for snap polls.
However, Mr. Wickremesinghe's UNP claims that Mr. Sirisena will be left with no choice as he would be the man who will command the confidence in the House.