Council tax payers face having to foot a £2.5 million bill because of a shortfall in one of Sussex's biggest local government pension schemes.

Auditors said the money needed to be pumped into the West Sussex County Council pension fund because of poor investment returns.

A total of 69 organisations are members of the £800 million fund, among them the county council, all of West Sussex's seven district and borough councils and Sussex Police.

The Local Government Association, the national lobby group which represents councils, is a member, as are most parish and town councils in West Sussex.

A revaluation presented to the council in the last few weeks said the fund's investment returns had been poor and the outlook was not good.

It identified a £2.5 million hole in the scheme's final salary scheme, which guarantees up to half a contributor's final salary plus a tax-free lump sum.

All final salary pension schemes are being squeezed as people live longer and interest rates fall.

The funds need enough money to pay existing pensioners and new members and most have been hit by a fall in share prices.

A county council spokeswoman said the authority had asked the Government to provide money to meet the shortfall.

Other councils facing similar problems with their pension funds are also lobbying ministers.

She said council tax payers would have to meet the £2.5 million shortfall over the next three years if no cash was forthcoming.

She said: "We feel that Government should be providing more money in our grant, which would actually make that up.

"It may be that the Government gives us so much but then it may be that we need to raise more council tax but at the moment we are lobbying Government on that."

The pensions watchdog, the Brighton-based Occupational Pensions Regulatory Authority (Opra), said problems with final salary funds were temporary but fund-holders were legally obliged to make up any shortfall.