Northern Rock's share price tumbled further today, prompting brief trading suspensions on the London Stock Exchange (LSE).
The latest fall in the value of the beleaguered lender's stock comes after the company revealed yesterday proposals it had received from potential suitors were "materially below" its current market price.
Northern Rock also confirmed it had yet to receive a bid for its entire business.
However a report today claims US buyout firm JC Flowers has submitted a bid for the Newcastle-based bank which would include an offer to its shareholders at a "nominal value".
A person said to be familiar with the situation told the Reuters news agency the offer included the proposed repayment of £15 billion in emergency loans to the Bank of England and the repayment of further debts to the institution over time.
Responding to the report, a Northern Rock spokesman said the company was not discussing any individual proposals with the media and said the lender had "nothing to add" to previous statements made in regard to the current review of its business.
Earlier in the day shares in Northern Rock tumbled by more than 40 per cent at one point, mirroring the 21 per cent fall in the company's share price yesterday.
The latest falls come after reports that private equity group Cerberus is no longer interested in Northern Rock, denting hopes of a rescue package materialising for the lender.
Britain's fifth-largest mortgage lender has not named its suitors, but confirmed yesterday it had received two types of proposals from those interested in the company both plans to invest in Northern Rock, including through the injection of assets and new capital, and proposals to acquire parts of the business.
A consortium led by Sir Richard Branson's Virgin group and an investment group headed by the former boss of Abbey are thought to be among those interested in taking control of the lender.
Yesterday chancellor Alistair Darling defended his handling of the Northern Rock crisis and told MPs the bank should be allowed time to consider its strategic options, adding that any solution to the lender's woes would be assessed by the government to ensure it "safeguards both the public interest and the specific interests of the taxpayer".
His comments came after the Treasury warned there was no certainty that current emergency loan facilities provided by the Bank of England would still be available to Northern Rock's owners by February with European state aid rules a potential bar to an extension of the facility in its existing form.
Northern Rock first turned to the central bank for an emergency loan in September, in the wake of this summer's global credit crunch.
The move prompted the first run on a British bank in almost 150 years, forcing the government to guarantee the savings of Northern Rock customers in order to restore confidence in the UK banking system.