The 20th Amendment must be passed by a two-thirds majority in Parliament.
The attorney general has said a referendum is not necessary but must be passed by a two-thirds majority in parliament.
However, the ruling Sri Lanka People’s Front does not represent a 2/3 majority in parliament.
The People’s Alliance has 145 elected members, out of which 143 will be elected when the Speaker and the imprisoned Choka Malli leave.
In addition, it has 148 members including Douglas Devananda, Athaulla and Pillayan who support the government.
The Speaker also has the opportunity to vote at a crucial moment, but he has 149 with him.