Fears of a fresh debt crisis in developing countries that would send shockwaves through the global financial system have been highlighted by a United Nations report stressing the vulnerability of poor states to falling commodity prices and higher interest rates.

The annual report from the UN conference on trade and development (Unctad) said the benefits of the debt relief provided to some of the world’s poorest countries as a result of the mass public campaigns of the late-90s and early 2000s were “fast evaporating”.

It said a number of countries – mainly in sub-Saharan Africa – had been forced to seek help from the International Monetary Fund and the World Bank, adding that the international community needed to be better prepared to manage a new crisis.

According to the IMF, 36 countries had received financial assistance worth $76bn under the Heavily Indebted Poor Country initiative, but Unctad said rushed attempts to integrate poorer countries into international financial markets after the 2008 global recession had left them vulnerable.

“Easy access to cheap credit in boom times has led to growing debt levels across the developing world. Developing country external debt stocks alone rose from $2.1tn in 2000 to $6.8tn in 2015, while overall debt levels rose by over $31tn between 2000 and 2014, with total debt-to-GDP ratios in many developing countries reaching over 120% and in some emerging economies over 200%.”

Many developing countries borrowed heavily when commodity prices were booming in the years after the 2008 financial crisis, and Unctad said the falling cost of oil, metals and food has made it harder for them to repay their debts. The threat of higher US interest rates after a prolonged period of sluggish growth in the west would add to the problems of the most heavily exposed countries, it said.

“Only a couple of years ago, the amount of debt that low-income developing countries could have sold to eager investors seemed almost limitless. International sovereign bond issuance in these economies rose from a mere $2bn in 2009 to almost $18bn in 2014,” Unctad said.

“But a prolonged commodity price shock, steep currency depreciations and worsening growth prospects in a deteriorating global economic environment have quickly driven up borrowing costs and debt-to-GDP ratios.”

The risk of a new debt crisis will be discussed when the IMF and the Bank hold their annual meetings in Washington next month. Unctad expects growth in Africa this year to be 2.8%, less than half the 6.7% recorded in 2010. Over the same period, growth in the world economy had eased from 4.1% to a predicted 2.3% this year.

“If the global economy were to slow down more sharply, a significant share of developing country debt incurred since 2008 – not only debt issued and held within the borders of individual economies, but also cross-border debt, including debt accumulated by private residents and governments – could become unpayable and exert considerable pressure on the financial system. Thus, the international community will need to to prepare itself for managing debt work-outs in a faster, fairer and more orderly manner than it has done so far,” it said.

“Already, several countries have turned to multilateral lending institutions, such as the IMF and the World Bank, in order to obtain financial assistance: Angola, Azerbaijan, Ghana, Kenya, Mozambique, Nigeria, Zambia and Zimbabwe have already asked for bailouts or are in talks to do so.”

The trade and development report said that against a backdrop of falling commodity prices and slackening growth in the developed world, borrowing costs for poor countries had been “driven up very quickly, turning what seemed reasonable debt burdens under favourable conditions into largely unsustainable debt.

“But the pro-cyclical nature of capital flows – cheap during a boom and expensive during downturns – is not the only drawback. Once a crisis looms, currency devaluations to improve export prospects simultaneously increase the value of foreign currency denominated debt.”

Unctad said developing countries had thought for a time that they were decoupled from the slow growth in the west, but were “increasingly worried that policy actions in the latter could trigger a deflationary spiral and a new round of debt crises”.