Calling for normal functioning of parliament, the Samajwadi Party (SP), the Left parties and the Telugu Desam Party (TDP) said Thursday that a Supreme Court judge should investigate the coal block allocations scam.
The four parties will demonstrate in the Parliament House complex Friday.
"A scam has occurred (in coal block allocation). There should be a probe and the guilty should be punished," SP chief Mulayam Singh Yadav said.
Addressing journalists along with leaders of other parties, he said they will also be demanding that the two houses be allowed to function normally to discuss the report of the Comptroller and Auditor General (CAG) into coal block allocations.
"Parliament should function, there should be discussion," he said.
He said they would talk to leaders of other parties to seek their support.
CPI-M leader Basudeb Acharia said the "coal scam is bigger than the 2G (spectrum) scam".
Prime Minister Manmohan Singh, he added, had to take responsibility as he was in charge of coal portfolio for a major part between 2004 and 2009 when the irregularities took place.
"The way there has been wrong allotment, it should be probed and the guilty punished," Acharia said.
He alleged there was "match-fixing" between the BJP and Congress and both the parties did not want a debate.
Acharia demanded cancellation of the coal blocks allocated "in a wrong way".
The BJP has been stalling parliament since last week over its demand for the resignation of the prime minister following the official auditor's report.