"President Rajapakse's intentional violation of the constitution is an impeachable offence," said Elmo Perera, an OPA member, a joint media conference with a number of other civil society groups.
The government has come under increasing criticism for rampant corruption, disregard for the rule of law by high-ranking government ministers and attacks on journalists and other critics.
The civil society groups which included the Sri Lankan branch of Transparency International, a corruption watch dog, warned that the government was becoming increasing intolerant of criticism and was heading towards a dictatorship.
Sunanda Deshapriya of the Free Media Movement said it was the government's own abuse of power and disregard for the rule of law that was bringing Sri Lank