"But I don't have any evidence," he added.
"It should be investigated why the Delhi police were inactive when the CM and other ministers were attacked by CPI(M) hooligans," Mukherjee said.
He also wondered at the police not being able to handle 20 to 22 SFI members and questioned how they could counter terrorists. "Delhi is totally unsafe."
Accusing SFI All India General Secretary Ritabrata Banerjee of direct involvement, Mukherjee said though an FIR was lodged against him and others at the Parliament Street police station, there has been no arrest as yet.
He said though senior CPI(M) leaders condemned the incident, the mood of the party rank and file was different.
On the attacks on CPI(M) party offices in the state, Mukherjee said "such a sentiment is obvious, after all they are human beings, but in general they restrained themselves."