Some of Europe's largest companies including car rental company Avis, UK retailer Debenhams and Spanish construction group Ferrovial, owner of UK airport operator BAA, are in danger of breaching their debt covenants and may increase the risk borne by their creditors, according to new research.

Of non-financial European companies with a market capitalisation higher than $500m (€370m), 28 could breach their covenants as a result of their deep exposure to debt and "poor liquidity", according to a study from risk consultancy RiskMetrics.