Speaking to media persons here, Ramesh alleged that the Trinamool has never given clear signals that it would never go with the Bharatiya Janata Party (BJP) or the Rashtriya Swayamsevak Sangh.
"We cannot align with a political party which ensures the withdrawal of the BJP candidate by entering into an understanding with the BJP, and wins a seat," Ramesh said at the state Congress headquarters Bidhan Bhavan, referring to the Howrah Lok Sabha by-election.
"Communal force is not only the one which is associated with the RSS. Communal force is also the one which meets BJP leaders, forms an understanding, and never gives clear-cut signal that they will never go with the BJP or the RSS," he said.
In the June byelection, Trinamool candidate and former international footballer Prasun Banerjee defeated Left Front spearhead Communist Party of India-Marxist candidate Sridip Bhattacharya.
The BJP opted out of the race after naming its former state president Asim Ghosh as the party candidate.
The Left Front and the Congress alleged that the BJP called it quits after secret parleys with the Trinamool.
The Congress and the Trinamool fought the 2009 Lok Sabha and the 2011 state assembly polls as allies, but their tie-up ended in September last year after the Trinamool exited the United Progressive Alliance - II.