The costs of rising life expectancy added billions of pounds to the pensions bills of the UK's top 100 companies during 2009, as they increased their provisions against this expense for the fourth year running.

The consultancy Mercer, which advises firms on their pension schemes, collated the financial estimates and predictions used by companies to gauge how big their pensions bills are likely to be. The survey covered the 44 members of the FTSE 100 that report results as of December 31.