Autonomy has struck a $70m (£35m) deal with a large global bank, by far its largest contract to date and the first concrete sign that the search software company could benefit from the US subprime lending crisis.

The deal, believed to be with Citigroup, is for software that allows businesses to quickly retrieve documents for lawsuits. Banks are thought to be growing increasingly worried about facing shareholder litigation over the losses they have taken on subprime home loans and are setting their internal computer systems in order to meet any legal demands.