Amnesty International last week called on
The human rights group urged both the government and the Tamil Tigers to allow international monitors into the northern Vanni region, which has seen intense fighting over recent weeks.
It also had other criticisms of both sides in the fighting. It accused the Tigers of using the displaced as a "deliberate buffer" against government forces.
Amnesty called on the Tamil Tigers "to ensure freedom of movement for civilians and stop preventing people from moving to safer places".
"These families must not be forgotten and left to suffer in a war zone."
Amnesty says that thousands of people displaced by the conflict are currently "in desperate need of shelter, food and sanitation".
"As the north-east monsoon season approaches, only 2,100 temporary shelters for 4,000 families have been provided, leaving at least 20,000 families in need of protection from the elements," a statement released by the group says.
"Around two-thirds of the civilian population of the Vanni region have been forced out of their homes,” the report said.
The human rights group says that unless food is distributed by aid agencies - rather than the government - "there is no way of establishing if the aid is reaching those most in need".
The Sri Lankan government responded by accusing Amnesty of publishing "outright falsehood" and charged that it was trying to show the government in an unfavourable light.
Amnesty’s account is " littered with misleading innuendo compounded by outright falsehood," the government says.
"It becomes clear that the intent of the report is to present a skewed picture unfavourable to the lawfully elected and popularly mandated government of
The government says the Amnesty report "is unfortunately yet another attempt to distort the factual situation pertaining to the conditions in which civilians in the north of
In September the government ordered all aid agencies to leave LTTE-controlled areas, saying that it could no longer guarantee the safety of aid workers in the area.
Since then the government has sent in food convoys to the region and the UN has been allowed to send some convoys. It argues that the United Nations believes that food supplies to the north are "satisfactory".
Among its criticisms of Amnesty, the government says its figure of 300,000 displaced people is an exaggeration and international monitoring of the situation in the north comes from international personnel who have travelled on the food convoys.
Amnesty told the BBC that it stands by its report.
Sam Zarifi, Amnesty's Asia Pacific Director, said in reply that: "The government seems to be quibbling over some of the numbers used in the report."
He told the BBC News website that the number of people at risk in the north was "staggering".
On the disputed issue of how much food is getting to the displaced, Mr Zarifi said "a quick needs assessment by international neutral monitors will establish the accuracy of the government's statements".
"We completely stand by our report," Mr Zarifi said.
"The government seems to be of the opinion that our criticisms of the Tamil Tigers are fair, but our criticisms of the government betray a bias in favour of the Tigers."
