Credit strategists are increasingly disturbed by a sudden and rare contraction of US bank lending, fearing a synchronised slowdown in the US and China this year that could catch euphoric markets badly off guard.

One key measure of US corporate borrowing is falling at the fastest rate since the onset of the Lehman Brothers crisis. Money supply growth in the US has also slowed markedly. These monetary and credit signals tend to be leading indicators for the real economy.

Data from the US Federal Reserve shows that the $2 trillion market for commercial and industrial loans peaked in December. The sector has weakened abruptly as lenders tighten credit, especially for non-residential property. Over the last three months it has dropped at a rate of 5.4pc on annual basis, a pace of decline not seen since December 2008.