The CPI-M Thursday demanded a high-level probe into reports that CBI director Ranjit Sinha met a number of people being probed by the agency at his residence.
This "raises disturbing questions", the Communist Party of India-Marxist said in a statement.
"Some persons (who met Sinha) were charge-sheeted by the agency and some have dubious antecedents," it said.
"It is highly improper and irregular for the head of the premier investigating agency to be meeting such persons and that too at his residence.
"There has to be a high-level probe into the matter and suitable action taken thereafter."