Final salary pension schemes face their worst ever deficits if plans go ahead for new accounting standards and more generous assumptions about life expectancy, pensions consultancy Aon has warned.

The top 200 schemes in February recorded their largest ever surplus of £21bn. However, a "double whammy" of proposals from the Accounting Standards Board and pressure from the pensions regulator for what it sees as more realistic assumptions about longevity "throws the future of final salary schemes into doubt", said Marcus Hurd, a senior actuary at Aon.