Pranab's telephoning Suman drew protest from TMC which accused the Finance Minister of trying to break the party, a charge denied by Congress.
"Pranab M directly called up a TMC MP seeking support. Politically ethical to do? Or trying to break TMC? Try & try again. Won't break," Trinamool Congress MP Derek O'Brien said on micro blogging site Twitter.
Suman later said the the union Finance Minister telephoned him to inquire about his health and not to seek his vote.
"Will a person of the stature of Pranab Mukherjee ring me up to seek my vote? He never asked me for my vote. But I want him to be President. He has vision," Suman said.
Senior TMC leader and West Bengal minister Subrata Mukherjee claimed Mukherjee was trying to break the party.
"This is unethical. Mukherjee should have rung up the TC chief Mamata Banerjee," he said.
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"It is unfortunate and unethical to make such a phone call to an individual MP or MLA," Urban Development Minister and a close aide of the TC supremo, Firhad Hakim told reporters.
Another TMC party MP and Union Minister of State for Tourism Sultan Ahmed also expressed unhappiness over the development, saying Mukherjee should not speak to individual leaders of Trinamool but its chief Mamata Banerjee.
Reacting to this, Congress spokesman Rashid Alvi said "why should we break their party? They are our allies... We have never done it."