It said Silva assaulted two journalists from the privately-owned Sirasa television network in full view of the police, a larger number of other VIPs and the general public.
The assault took place on Monday at the opening of a new flyover bridge in Kelaniya, Silva's constituency north of Colombo.
"We note with deep regret that not a single police officer present when this incident took place intervened to stop the attack by the Minister," the FMM said.
Silva and his "coterie of murderous thugs" had assaulted Sirasa TV journalists Thushara Saliya Ranawaka and video cameramen Waruna Sampath and seized their cameras.
"Sirasa TV footage of the attack shows very clearly that it was the Minister who led the attack," the statement said.
"The Minister’s snarling threat, that he will have to break the Buddhist teaching of