Wimal Weerawansa, the Minister of Housing and the leader of the nationalist Freedom Front (NFF), held its May Day rally separately from the ruling United People's Freedom Alliance's main rally.
"We are opposed to northern election being held as it would lead to the creation of a separate state (Tamil)", Weerawansa said.
"We want to create an awareness on the dangers posed by the setting up of the northern provincial council", Weerawansa added.
President Mahinda Rajapaksa has vowed to hold the Northern Provincial Council election in September.
However the Sinhala majority nationalist and hardline groups are opposing the move, saying the Tamil National Alliance (TNA) would further their separatist agenda after winning the election.