He said the government must go to the people for confirmation on whether the president made the correct decision when he appointed him as prime minister.
Keheliya Rambukwella, a spokesman for Sirisena's government, said the president's coalition had the backing of 105 lawmakers as of Friday, eight short of a parliamentary majority.
Global concern has grown over the mounting turmoil, with Wickremesinghe refusing to leave the premier's official residence while the president also suspended parliament to head off any revolt against his action.
Deepening the political crisis he created two weeks ago, Sri Lanka President Maithripala Sirisena in an extraordinary Gazette notification announced the dissolution of the parliament with effect from Midnight Friday and scheduled general elections to be held on 5th January 2019.
Rajapakse and the ousted Wickremesinghe have been battling for power for two weeks as worldwide concern grew over the mounting turmoil in the strategically important island nation.More news: Trump hints at potential federal role in Florida recount
Sirisena had suspended the assembly's work until mid-November when first moving against his prime minister.
Independent legal experts said parliament could be dissolved only after four-and-half-years from the date of the Aug 2015 parliamentary election, either through a referendum, or with the consent of two-third of lawmakers.
Sirisena's United People's Freedom Alliance (UPFA) admitted ahead of the president's stunning announcement that they had failed to secure enough cross-over MPs to win a confidence vote in the House.
The leftist People's Liberation Front (JVP), which regards the sacking of Wickremesinghe as unconstitutional, accused Sirisena of trying to consolidate his power grab.
The president was acting well within his constitutional rights in dismissing the parliament, Jayasekara stressed, adding: "The best thing is do now is go for an election".More news: Would Two Flu Shots Protect Me Better Than One?
This is despite several legislators saying they were offered millions of dollars to switch allegiance. He has refused to vacate his official residence and demanded that Parliament be summoned immediately to prove he had support among its members.
He and his allies have 120 MPs while Rajapakse and Sirisena have 104. The speaker, the 225th member, is neutral. However, on November 1, he lifted the suspension after coming under severe criticism.
The EU, in a joint statement with Norway and Switzerland, called for parliament to reconvene and hold an immediate vote.
Jayasuriya said this week he can't recognize Rajapaksa until he demonstrates a majority in the legislature.
Wickremesinghe had late Thursday thanked his supporters in a Facebook video for not letting Sri Lanka be "plunged into the darkness of dictatorship".More news: Drawn Lions series makes England Test bigger for All Blacks - Hansen
The power struggle on the island of 21 million people has paralysed much of the administration, according to legislators on both sides of the dispute.