The UK Minister of State for Asia and the Pacific Mark Field said that he was concerned by news that Sri Lanka's Parliament has been dissolved days before it was due to be reconvened.
Under pressure from the local as well as worldwide organizations including the United Nations, European Union and Western governments, the President chose to reconvene the parliament on November 14, just two days ahead of the scheduled date.
Wickremesinghe insisted his firing is unconstitutional. He has refused to vacate his official residence and demanded that Parliament be summoned immediately to prove he had support among its members.
The move comes after an intense power struggle in the past two weeks which followed Sirisena's sudden sacking of Prime Minister Ranil Wickremesinghe and the appointment of former leader Mahinda Rajapaksa.
Mr Sirisena has also accused Mr Wickremesinghe and another Cabinet member of plotting to assassinate him, a charge Mr Wickremesinghe repeatedly denied.
Sirisena was critical of investigations into military personnel accused of human rights violations during Sri Lanka's long civil war against a Tamil separatist group, which ended in 2009.
Perera said the dissolution was carried out so that Sirisena could avoid defeat in parliament next week.More news: Dez Bryant injury: WR suffers apparent Achilles tear at practice
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Sirisena signed a decree dismissing the legislature in a bid to head off any revolt against his actions which included suspending parliament for almost three weeks.
Jayasuriya said this week he can't recognize Rajapaksa until he demonstrates a majority in the legislature. However, the decision to dissolve the house shows otherwise, observers say. The current Parliament was elected in August 2015. "We will fight this dictator to the end".
Sirisena had said on Monday that he had the support of 113 legislators when he sacked Wickremesinghe.
Sri Lanka's President Maithripala Sirisena on Friday dissolved parliament and called a snap election after failing to gain enough support for his nominee for prime minister, deepening the island's political crisis with a gamble deemed illegal by the ousted premier's party.
Mark Field, the British minister of State for Asia and the Pacific, said: "As a friend of Sri Lanka, the United Kingdom calls on all parties to uphold the constitution and respect democratic institutions and processes". The only other legal ways would be through a referendum, or with the consent of two thirds of lawmakers. "We will be fighting this to ensure that Democracy reigns supreme in the country", the party said on Twitter.
Rajapaksa indicated what was coming hours before the dissolution in a speech.
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".