The decision was reached after a parliamentary group meeting of UNF Saturday morning and the case will be filed on Monday.
UNF and some smaller parties termed the move as illegal, unconstitutional and unacceptable.
The new governmen has sought to defend the dissolution saying President is empowered to do so.
President Maithripala Sirisena had dissolved the Parliament through a gazette notification last night and called for elections on fifth of January.
Parliament term was to expire in August 2020 and early elections has been called almost 20 months before it was due.
The move comes exactly two weeks after the President has appointed Mahinda Rajapaksa as new Prime minister replacing Ranil Wickremsinghe.
As per the 19th amendment to the constitution, President was not empowered to dissolve the parliament till completion of four and half years of its term or till two thirds of the house recommended for dissolution.
The last Parliamentary elections were held in August 2015 which did not give clear majority to either of two main parties.
However, both parties of Sirisena and Wickremsinghe had come together to form a national unity government which broke down on 26th of last month leading to crisis.