They also said the resignation was "too little" and "too late" and that the CBI presented the "true facts" with regard to the 2G Spectrum scam only because the investigations are being monitored by the Supreme Court.
The BJP said Maran`s resignation was "long overdue" and demanded that Home Minister P Chidambaram too should follow suit.
"P Chidambaram should resign. We have already demanded this as the 2G spectrum scam could not have occured had the Finance Ministry (then headed by him) not changed its stand on the issue of auctioning radiowaves," BJP spokesperson Prakash Javadekar said today.
On Maran, Javadekar said he should have resigned long back and asked why does the Prime Minister delay the removal of "corrupt members" of his team.
"Initially, efforts are made to defend them. When all routes are exhausted, action is taken," he said.
In Chennai, AIADMK chief J Jayalalithaa said it was long overdue and that the Prime Minister should have made him quit earlier.
"This is something long overdue. The Prime Minister should have made him to resign long ago," she said.
CPI(M) politburo member Brinda Karat said Maran resigned because there was no alternative for him and sought an explanation from the Prime Minister on the issue.
CPI leader D Raja termed the resignation of Maran as "too late" and sought Prime Minister`s explanation on the development.
"The resignation of Maran is too late.He should have done long time back as the allegations are very serious. Now it is for the Prime Minister to explain to the people and to Parliaent," he said.
He said with the series of scandals, the UPA-II government stood thoroughly exposed.