WASHINGTON, Nov 10 (Reuters) - Existing systems for tracking the sovereign debts of the poorest countries are inadequate and mask hidden debts, and they are likely to owe far more than the record levels currently estimated, World Bank chief economist Carmen Reinhart said. The multilateral development bank on Wednesday released the first comprehensive assessment of global and national debt surveillance systems, saying it found “massive gaps” in the ability to track how much each country owes - and to whom. The current patchwork of databases - with different standards and definitions - meant debt estimates could be off by as much as 30% of a country’s gross domestic product, the report found, noting that 40% of low-income countries had published no data on their sovereign debt at all for over two years. The World Bank, long critical of the lending practices of China, the world"s biggest creditor, last month said the debt burden of low-income countries rose 12% to a record $860 billion here in 2020, and called for comprehensive efforts to help low- and middle-income countries reach more sustainable debt levels. Reinhart told Reuters the actual number could be “markedly higher” and said the new study underscored the need for reforms to ensure better debt statistics, coordinated data collection, and integrated debt management systems. She said the opaque nature of many debt contracts and the private sector’s complete failure to participate in a G20 debt relief initiative clouded the prospects for timely debt restructuring efforts for low- and middle-income countries. The bank estimates 12% of low-income countries are already in debt distress, and 44% are at high risk of getting there. BIGGER SHARE OF GLOBAL GDP The potential default of a poor country like Chad - the first country to seek restructuring under the G20’s Common Framework - would not affect the global financial system, but even middle income countries faced growing risks, and that could ultimately affect global growth prospects, she said. Developing economies, including China, now account for 60% of global GDP, up from less than 40% during the last big debt crisis of the 1980s, which means that a new debt crisis could have a significant impact on the global economy, she said. “Collectively, you’ve got to care. This is a much more substantive share of the global activities,” she said. Reinhart said her past research on China’s lending showed that official debt statistics captured about half of the actual debts, and fluctuating commodity prices and the continued impact of the COVID-19 pandemic could drive debt levels up further. Possible interest rates hikes on the horizon in richer economies could exacerbate challenges for developing countries, she said, since they could siphon off investment and raise the already high cost of borrowing. Debt service payments, related to exports, doubled to over 20% in 2020, she said, reflecting the rising toll that increased borrowing is taking on the poorest countries. She said 54% of over 70 countries surveyed by the World Bank did not have consolidated fiscal accounts that provided a “cohesive big picture” of central bank debt and state-owned enterprises, another factor obscuring true debt levels. There was also limited data on increasingly popular resource-backed loans, which use future revenue as collateral, and central bank repurchases and foreign-currency swaps that low-income countries were using to support external borrowing. (Reporting by Andrea Shalal; Editing by Simon Cameron-Moore)