"He is likely to be suspended from the party after President Amit Shah returns from AIIMS. He has now crossed all the limits as he directly attacked Prime Minister Narendra Modi," a senior BJP functionary said.

Party spokesperson Rajiv Pratap Rudy called Sinha an "opportunist" and said: "The party would take congnisance of it."

Rudy, who like Sinha also hails from Bihar, alleged that the MP from Patna Sahib constituency is availing all facilities provided to a Member of Parliament.

"Some people want to carry the banner of BJP to enjoy the perks of being an MP. Such people make it a point to be present in Parliament when the party issues whip, so that they do not lose membership (of the House). But at the same time, they are so opportunist ... they voice different opinions from different platforms," he told a press conference.

Calling him "very clever", Rudy accused Sinha of never being present in any BJP activity in the last five years.

"I have never seen him present in any party activity for the last five years. He is very clever and takes decisions on the basis of his political understanding. He calls himself of BJP and attends opposition rallies. So, I am sure the party will definitely take a call on it," he added.

Bihar BJP President Nityanand Rai told IANS that "appropriate action will be taken at appropriate time."

Meanwhile, Sinha -- who attended on Saturday an anti-BJP rally organised by Trinamool Congress chief and West Bengal Chief Minister Mamata Banerjee at Brigade Parade Ground in Kolkata where leaders of 23 opposition parties were present -- said he would not mind if he is ousted from the BJP.

"I dont't mind if am ousted (from the party). I am in BJP because of people of the country. So, what I say or do is in the interest of the country," Sinha said.

Speaking on the Rafale controversy, he said: "I am not saying you are guilty, neither saying you are innocent. But if things are not answered, people will say 'chowkidaar chor hai'."

Sinha has been speaking against the party and has been critical of government's decisions like GST and demonetisation.