A $19 trillion corporate debt mountain built up by reckless lenders seeking higher returns threatens to topple over and deepen the next recession, the International Monetary Fund has warned.

The global lender of last resort sounded the alarm on a boom in corporate lending in the US and China, with debt classified as high-risk accounting for almost half of the market in the world’s two biggest economies.

The IMF said in its Global Financial Stability Report that in eight major economies including the UK, debt-at-risk - or money owed by companies which cannot cover the interest payments with profits - would hit $19 trillion in the next downturn, or 40pc of the total amount owed by businesses.

That is above levels seen in the financial crisis, despite the shock tested by the Washington-based institution being just half as severe as the last recession.

The UK is one of the economies most at risk from its large share of junk-rated debt.