Tiwari flagged off a BJP bike rally in the Yamuna Vihar area in his North East Delhi Lok Sabha constituency on Saturday wearing military fatigues.
Drawing flak, Tiwari tweeted on Sunday, "I wore (it) simply because I felt proud of my Army. I am not in Indian army but I was expressing my feeling of solidarity. Why should it be treated like an insult? I have the highest regard for our Army. By (this) logic, tomorrow if I wear a Nehru Jacket, will it be an insult to Jawaharlal Nehru?"
Trinamool Congress MP Derek O'Brien said it was a "shameless act" on Tiwari's part.
"Shameless. Shameless. Shameless. Manoj Tewari BJP MP and Delhi President wearing Armed Forces uniform and seeking votes. BJP-Modi-Shah insulting and politicising our jawans. And then giving lectures on patriotism. Low life," he tweeted, targeting Prime Minister Narendra Modi and BJP president Amit Shah.