A Sri Lankan court on Monday barred Mahinda Rajapaksa from acting as the Prime Minister, in a major setback to the President Maithripala Sirisena who had installed his former rival in the place of Ranil Wickremesinghe in a controversial decision that triggered a constitutional crisis in the island nation.

The Court of Appeal temporary halted Rajapaksa and his Cabinet from functioning in their positions in response to a case filed by 122 legislators against the disputed government.

The court set the hearing of the case for December 12 and 13.

"According to the interim relief, Rajapaksa and his disputed government have been prevented from acting as PM, cabinet and deputy ministers," said a lawyer, who was present at the hearing.

He added that the court was of the opinion that "irreparable damage" could be caused if persons not entitled to do so sit as prime minister and cabinet ministers.

As many as 122 parliamentarians of Wickremesinghe'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.

The interim ruling was a major blow to both President Sirisena and Rajapaksa after the former had appointed the latter as the prime minister on October 26, plunging the country into constitutional crisis.

Sirisena later dissolved Parliament, almost 20 months before its term was to end, and ordered a snap election. The Supreme Court overturned Sirisena's decision to dissolve Parliament and halted the preparations for snap polls.

The political crisis has crippled the government for more than a month.

Both Wickremesinghe and Rajapaksa claim to be the prime ministers. Wickremesinghe says his dismissal is invalid because he still holds a majority in the 225-member Parliament.

Prior to the crisis, Wickramasinghe's UNP had the backing of 106 parliamentarians while Rajapaksa and Sirisena combine had 95 seats.

Rajapaksa has, so far, failed to prove his majority in Parliament.

Wickremesinghe, with the support from the main Tamil party, claims to have the support of more than 113 legislators, required for simple majority.

The Tamil National Alliance (TNA) has 16 seats in the house and JVP has six legislators.

The UNF has moved three no trust motions against Rajapaksa, who has refused to step down.

The Sri Lankan president has said that due to sharp personal differences with Wickremesinghe he would not reappoint him as the Prime Minister.

However, Wickremesinghe's UNP claims that Sirisena will be left with no choice as he would be the man who will command the confidence in the House.