Tyco, the US conglomerate, and Vivendi, the French media group, are two of 23 companies that could face a liquidity crunch if their ratings fall much further, according to a new rating agency report.

Standard & Poor's, the rating agency, has published a danger list of 23 companies in the US and Europe whose loans and bonds carry clauses demanding repayment if the company's ratings fall, or if other measures of financial health deteriorate.