Liffe, the derivatives arm of NYSE Euronext, is to launch new money market contracts in response to growing doubts over the validity of Libor, the benchmark rate banks charge to lend to each other, and Euribor, its eurozone equivalent.

The London-based exchange will launch new futures contracts linked to Sonia and Eonia, alternative sterling and euro funding indexes in June. Sonia and Eonia are the sterling and euro Overnight Interbank Averages, the weighted averages of actual overnight deposit rates.