The death toll from Sudan's Darfur crisis has been grossly underestimated, British MPs have said.
The world has failed the people of Darfur, the MPs say
They said deaths could reach 300,000 - more than four times the World Health Organization's figure of 70,000.
The International Development Committee report also said the world's response had been "scandalously ineffective".
Sudan's government and Arab militias are accused of war crimes against the region's black African population.
The US says the crisis which erupted in 2003 amounts to genocide.
More than two million people are estimated to have fled their homes during the crisis.
The committee said events in Darfur were "no less serious and heinous than genocide".
It said responsibility for the conflict lay mostly with the Sudanese authorities.
The report said the WHO's figure of 70,000 deaths was inaccurate as it only included violent deaths that took place in camps for internally displaced Sudanese.
Of those attacked in their settlements, only those who made it to the camps before dying would have been counted, the MPs said.
And the WHO figure only covers the period from March to mid-October 2004 and only takes account of deaths in accessible areas within Darfur's borders.
The committee added that other countries and the UN Security Council must also take some of the blame for the situation.
This was because:
Early warnings about the crisis were ignored.
Humanitarian organisations were slow to respond.
Guidelines for managing the camps were unclear.
The UN suffered from an "avoidable leadership vacuum" in Sudan at a crucial time.
Priority given to Sudan's north-south peace process was "misguided" and had "predictable and deadly" consequences for Darfur.
"After the genocide in Rwanda, the world said 'never again'," committee chairman Tony Baldry MP said.
"President Bush said that genocide would not be allowed to happen 'on his watch'. These words should mean something.
"The international community must now fulfil its responsibility to protect the people of Darfur. We demand that there is action now."
The committee recommended that the situation should be referred to the International Criminal Court and said that there should be sanctions and an extension of the arms ban to cover the Sudanese government.
Later International Development Secretary Hilary Benn told Channel Four News the truth was that no-one knew the real Darfur death toll.
But he said countries were backing the African Union's support operation and the UK was providing humanitarian aid and urging a political solution.
"Of course, while people continue to die in Darfur the problem hasn't been solved," he said.
"And as far as those people are concerned, yes they want the international community to be doing more.
"But above all what they want are the people who are doing the fighting and the killing...to bring an end to the conflict."