Malawi Congress Party (MCP) President Lazarus Chakwera was sworn in as a Member of Parliament (MP) on Monday.
The swearing in ceremony of other remaining new MPs will take place on Tuesday at Parliament in Lilongwe.
Chakwera together with UTM president Saulos Chilima are challenging the declaration of President Peter Mutharika of Democratic Progressive Party (DPP) as the winner of the May 21 presidential election.
The first hearing of the case took place on Friday at the High Court in Lilongwe and the case will continue on Wednesday at the constitutional court.
The case is being presided over by High Court judges Mike Tembo, Dingiswayo Madise, Redson Kapindu, Ivy Kamanga and Healey Potani.