On Saturday the alliance said it would lobby neighbouring India and the international community to ensure the island's Tamil community - 12.5 per cent of the population -gets a greater say in the administration.
"Power sharing arrangements must be established ... based on a federal structure in a manner also acceptable to the Tamil-speaking Muslim people," the party said in its latest manifesto.
The Tamil Tigers agreed to a federal state in December 2002 but Norwegian-brokered talks collapsed in 2006, leading to more fighting that eventually resulted in their military defeat by government forces last year.
Between 80,000 and 100,000 people were killed in the fighting.
Tamils have long complained of discrimination at the hands of the island's majority Sinhalese, but Sri Lankan authorities have rejected any self-rule for them, saying it would be a prelude to secession.
Mahinda Rajapaksa, the Sri Lankan president, called the April parliamentary vote after being re-elected in January in a presidential election called two years ahead of schedule.
Sarath Fonseka, the opposition leader and former army chief, has been detained on sedition allegations.
The Tamil alliance, which supported Fonseka in the presidential election but plans to contest the parliamentary vote on an independent platform, also demanded resettlement, housing and livelihood programmes for the nearly 300,000 Tamil civilians displaced in the last stages of the civil war, about 100,000 of whom are still in refugee camps.
The Tamil National Alliance, a coalition of moderate Tamil parties, has 22 seats in
the outgoing parliament, but the various elements have split following the crushing of the Tigers, weakening their bargaining position.