The World Bank has said more people are living in extreme poverty in developing countries than previously thought as it adjusted the recognized yardstick for measuring global poverty to $1.25 a day from $1.

The poverty-fighting institution said there were 1.4 billion people a quarter of the developing world, living in extreme poverty on less than $1.25 a day in 2005. Last year, the World Bank said there were 1 billion people living under the previous $1 a day poverty mark. The new figures are likely to put fresh pressure on big donor countries to move more aggressively to combat global poverty, and on countries to introduce more-effective policies to help lift the poorest.

Even so, the new estimates show how progress has been made in helping the poor over the past 25 years. In 1981, 1.9 billion people were living below the new $1.25 a day poverty line. The new estimates are based on updated global price data, and the revision to the poverty line shows the cost of living in the developing world is higher than had been thought. The data is based on 675 household surveys in 116 countries.

"These new estimates are a major advance in poverty measurements because they are based on far better price data for assuring that the poverty lines are comparable across countries," said Martin Ravallion, director of the World Bank's Development Research Group. While the developing world has more poor people than previously believed, the World Bank's new chief economist, Justin Lin, said the world was still on target to meet a United Nations goal of halving the number of people in poverty by 2015.

However, excluding China from overall calculations, the world fails to meet the U.N. poverty targets, Lin said. The World Bank data shows that the number of people living below the $1.25 a day poverty line fell over nearly 25 years to 26 percent in 2005 from 52 percent in 1981, a decline on average of about 1 percent a year, he said.

Lin said the new poverty data meant there was no room for complacency and added that rich donor nations need to keep their promises of stepped-up aid to poor countries. "The sobering news that poverty is more pervasive than we thought means we must redouble our efforts, especially in sub-Saharan Africa," said Lin, a leading Chinese academic.

The new figures come ahead of an updated assessment of progress in meeting the U.N.'s Millennium Development Goals, which will released late next month at a meeting of the U.N. General Assembly. While most of the developing world has managed to reduce poverty, the rate in sub-Saharan Africa, the world's poorest region, has not changed in nearly 25 years, according to data using the new $1.25 a day poverty line.

Half of the people in sub-Saharan Africa were living below the poverty line in 2005, the same as in 1981. That means about 380 million people lived under the poverty line in 2005, compared with 200 million in 1981.