The world's wealthiest governments provided less aid last year and those countries needing most help got a smaller share of available funds, the Organisation for Economic Cooperation and Development said Wednesday.

Total aid from the 30 members of the OECD's Development Assistance Committee reached $153 billion in 2018, on a new "grant-equivalent" basis that takes into account the discounted value of funds promised for a future date.

Using the traditional cash-flow basis to measure grants and loans, aid stood at $149.3 billion, down 2.7 per cent from 2017.

The OECD, which promotes free-market economics, said the decline mainly reflected a drop in aid to help countries host refugees.

"This picture of stagnating public aid is particularly worrying as it follows data showing that private development flows are also declining," Angel Gurria, OECD  secretary general, said in a statement.

Aid to the least-developed countries was down 3.0 per cent last year, with money for Africa down 4.0 per cent. Humanitarian aid overall dropped 8.0 per cent.

"Less ODA is going to least-developed and African countries, where it is most needed," said Susanna Moorehead, head of the OECD's development committee.

She also called on donor countries to offer more grants or low-interest loans, as opposed to traditional market-rate loans.

Overall, 2018 aid represented 0.31 per cent of the combined gross national incomes for the 30 OECD donor countries, less than half their target of 0.7 per cent.

"The cut in aid to the poorest and most vulnerable countries is alarming. The world's richest nations cannot turn their backs on the poorest," said Julie Seghers, the OECD policy adviser at NGO Oxfam.

"It's shameful that most rich countries still fail to meet the level of development aid agreed over 50 years ago," she said.