Aid officials have called the situation in Darfur the world's most pressing humanitarian emergency and Britain's Secretary of State for International Development Hilary Benn said the response so far had been inadequate.
"The number of humanitarian agencies on the ground is limited. We need more," Benn told the House of Commons.
"I have also been concerned about the adequacy and speed of the UN's response, although this should now change."
Benn has just returned from the western Sudanese region, where militias have been driving out black Africans in what UN Emergency Relief Coordinator Jan Egeland has called a scorched-earth campaign of ethnic cleansing.
The United Nations estimates fighting in Darfur has affected more than two million people. More than half have been driven from their homes, with 130,000 fleeing into neighbouring Chad.
Benn, who announced at the weekend another 15 million pounds ($28 million) in funding on top of 19.5 million already given to U.N. agencies, said seasonal rains that had already started in Darfur would make matters worse by making roads impassable.
He said the main cause of the crisis was insecurity, and called on the Sudanese government to act quickly to restore calm and help in relief.
"The number of humanitarian agencies on the ground is limited. We need more ... I have also been concerned about the adequacy and speed of the UN's response, although this should now change"
Britain's Secretary of State for International Development
"We are in a race against time in Darfur, and the UK remains committed to doing all that it can to help those affected and to work for a just and lasting peace for its people," Benn said.
Sudan has been mired in civil war for all but 11 of the 48 years since its independence from Britain.
The Khartoum government and the rebel Sudan People's Liberation Movement (SPLM) signed a collection of protocols in May as a prelude to a comprehensive peace deal ending the war in the oil-rich south of the vast country, expected in August.
The southern conflict has killed more than two million people, driven four million more from their homes inside Sudan and another 600,000 into neighbouring states, according to the United Nations.