Uniq has 30 food production sites across Europe

In October, the UK firm announced unsolicited bid approaches - however only a single would-be suitor remains.

But issues over a �100m ($186m) pension plan black hole have to be resolved and an offer price has not been discussed.

Shares in Uniq, maker of ready meals, desserts and salads for supermarkets, closed down 9.34% at 165 pence.

Pension payment

"Discussions with one of these parties on pensions are continuing, although it has not yet been possible to resolve the issues surrounding the leveraged nature of the potential bidder's proposed capital structure in the context of the pension scheme liabilities," Uniq said in a statement.

The pension fund trustee is worried that any deal would harness Uniq with so much debt that it may be unable to fill the pension deficit.

The chances of a successful bid coming through look pretty limited Investec analyst Nicola Mallard Check Uniq's share price

Uniq also said it was boosting the amount of money it pays into the pension fund by �180m over 12 years.

It will pay an extra �15m a year into the scheme - a large increase on the �8.4m payment announced in December. The payment will be made on top of this year's normal contribution of �4.2m.

The firm also said that expectations for its current financial year to the end of March were unchanged, but profits for 2005/06 would be hit by tough trading conditions in its home market.

Costs review

Uniq, which employs 8,700 people at 30 sites across Europe including nine in the UK, is carrying out a review of its costs and group structure to help improve profitability.

However according to Investec analyst Nicola Mallard, who has a "hold" rating on Uniq: "The chances of a successful bid coming through look pretty limited."

Among the Buckinghamshire-based firm's retail customers is Marks & Spencer.

In autumn 2004 a strike at the Uniq Prepared Foods Plant in Annan, Scotland, was called off after staff were awarded a 5% pay rise.