The Tamil National Alliance (TNA) said a request for the cortege of slain Nadarajah Raviraj to travel to the northern peninsula of Jaffna by road was turned down by the government.
Raviraj, who was shot dead by unidentified gunmen in Colombo Friday morning represented the Jaffna district, 400 kilometres (250 miles) north of Colombo. He was a staunch human rights campaigner.
Defence officials confirmed the request was rejected, but said they offered air transport to Jaffna.
TNA leader R. Sampanthan said the party was making other arrangements to charter a private plane and hold the funeral at his home constituency of Chavakachcheri in Jaffna.
A large group of political parties and anti-war activists called for a day of protest Monday to denounce the slaying of Raviraj and said the killing in broad daylight demonstrated the level of lawlessness.
"We are fast becoming a country of widows," said Nimalka Fernando, a leading human rights activist. "These killers and the mighty terror of the state are making us a killing field."
"We cannot allow this country to be ruled in this manner," she said, adding the gunmen got away after stopping traffic in front of a military installation, without fear of being arrested.
"It is the culture of impunity that must stop," she added.
The main opposition United National Party (UNP) said the government must accept responsibility for the killing -- the second of a TNA legislator in a year -- and ensure the killers were brought to justice.
Tamil Tiger rebels conferred their highest civilian honour Saturday on Raviraj.
The rebel Liberation Tigers of Tamil Eelam (LTTE) said their chief Velupillai Prabhakaran bestowed the title of "Mamanithar," or great man, on Raviraj, who on the day before petitioned the United Nations to intervene and protect civilians caught in crossfire between the rebels and government fighting.
His Tamil National Alliance party was regarded a proxy of the Tigers, but Raviraj was regarded a moderate who had never taken up arms.
He spoke Sinhalese and was a personal friend of President Mahinda Rajapakse, who has asked the foreign ministry to invite British police to help probe the killing.
The killing was a serious breach of security in Colombo, where police and the armed forces have maintained a high state of alert for several weeks.
The killing comes during an upsurge in fighting on the island, with about 3,300 lives lost in the past year, despite a 2002 truce in the separatist conflict.

Copyright AFP (Agence France-Presse), 2006