Mahinda Samarasinghe, Sri Lanka's minister of disaster management and rights, told a special session of the 47-member UN Human Rights Council (UNHRC) in Geneva, Switzerland, on Wednesday that his government would help those displaced.
But he dismissed concerns raised by the ICRC and other aid agencies who have been kept out of some camps, including Manik Farm, which holds around 210,000 people.
"Access of course we will provide. And we have been doing so. And we intend to continue with it," Samarasinghe said.
The UNHRC session brushed aside calls to investigate allegations of war crimes by both sides in the final chapter of the fighting.
Sri Lanka's allies on the council, including China, Cuba and Egypt, forced through a resolution with 29 votes to 12 against and six abstentions.
The resolution condemned the Liberation Tigers of Tamil Eelam (LTTE) for using civilians as human shields and stressed that the war was a "domestic" matter that didn't warrant outside interference.
Western officials expressed dismay at the council's resolution.
Dante Martinelli, the Swiss representative, criticised the "worrying absence" and "significant gaps" in the text.
He noted that the text failed to make explicit reference to granting humanitarian groups "rapid access" to people displaced by the fighting.
The UNHRC has no enforcement power, but countries generally fight doggedly to avoid criticism and the negative attention that its resolutions bring.
'Sick of pressure'
Samarasinghe earlier said his government was sick and tired of foreign pressure.
"There is no reason for a probe. These are political statements made by various people," he told the AFP news agency.
But Navi Pillay, the UN high commissioner for human rights, told Al Jazeera it was a "reasonable call since very little information came to the world with the international media having been denied access into Sri Lanka.
"The information regarding the Sri Lankan conflict may come in bits and pieces but I think it will come out necessarily because there is a need to ensure justice for the victims and survivors there," she said on Wednesday.
Her comments came as the Sri Lankan government announced that it will maintain its state of emergency, which allows it to make arrests and seize evidence without warrants, despite the defeat of the separatist Tamil Tigers.-
Nimal Siripala, Sri Lanka's health minister, said the order would remain in place to prevent a resurgence of the LTTE.
Last week the government declared an end to its 26-year war against the Tamil Tigers after killing its leaders.
Under the state of emergency, police can arrest, enter homes and seize evidence without warrants and hold those they arrest for 18 months without trial.
The government said it suspects that suicide bombers remain in the capital Colombo and have adopted a low profile.
Veerasingham Anandasangaree, a Tamil politician, said it was unfair to keep the emergency powers in place, since most of the Tamil people "gave full support to the army to liberate them. If they are treated in this manner, there is no justice at all".
On Wednesday, Sri Lankan soldiers on a mission to flush out remnants of the LTTE killed 11 suspected fighters in jungles in the east of the country, the military said, in the largest clash since the army declared victory.