Pension schemes at Royal Mail and the BBC are among the latest to have been hit by turbulent market conditions in the last few months.

Royal Mail's pension accounting deficit has increased by more than £1bn from £2.9bn to £4bn since March as a result of heavy falls in the stock market. And the actuarial deficit, due to be revalued next year, is also expected to increase from its previous level of £3.4bn in March 2006.

Royal Mail's half-year trading statement read: "The urgent need to tackle this challenge is underlined by the continuing burden of the heavy cash contributions the company is required to pay towards the deficit and servicing the pension plan."

Meanwhile the BBC pension scheme has lost £1bn in value in less than for months. The scheme's assets reportedly stood at £7.98 billion at the end of June. It is thought that almost £2bn was invested in British equities, which are said to have dropped by 35%.

A BBC spokesman said: “The important thing for pension funds is the long term performance of the financial investments. The BBC pension scheme is not immune from market forces and the value of our assets fluctuates as markets rise and fall. The scheme is however well placed to ride out the storm. It has a diverse portfolio which provides a degree of protection. Both the BBC and trustees remain vigilant, are watchful of current markets and believe their approach to funding is appropriate to help maintain the scheme's security."