Carillion has put one of the big four accountancy firms on standby to oversee an administration of the construction giant in a further signal of the precarious state of its finances.
Sky News has learnt that EY and PricewaterhouseCoopers were asked to compete for the role as administrator to the HS2 high-speed rail-link contractor in recent weeks, with EY said to have been lined up by directors.
The move is part of contingency planning being undertaken by Carillion as it races to secure approximately £300m of emergency funding by the end of the month.
Shares in the struggling company fell sharply on the latest developments - down 15% in Friday afternoon trading.
The move does not necessarily mean that EY - which has been acting as an adviser on the company's rescue plan for several months - will ultimately be appointed, according to insiders.
It comes as Government officials and regulators hold crisis talks on Friday aimed at safeguarding the interests of more than 28,000 pension scheme members who could face cuts to retirement payments if Carillion does not survive.
Senior civil servants from the Cabinet Office are due to attend an emergency summit that will include representatives from The Pensions Regulator (TPR), Pension Protection Fund (PPF), Carillion's pension trustees and an assortment of City advisers.
The talks will take place 24 hours after a meeting of ministers from across a multitude of Whitehall departments, reported on Thursday by the Financial Times, to discuss contingency plans for its collapse.
A Downing Street spokesman said the Government was closely monitoring the unfolding situation.
Earlier this week, Carillion presented a revised business plan to scores of lenders - but contrary to reports, this was not expected to produce an instant agreement with them.
Carillion's shares rocketed on Monday when some in the City misinterpreted last weekend's story as a sign that a rescue deal was about to be agreed.
The company was then forced to issue a statement to the stock market that it knew of no reason for investors' sudden optimism.
Sky News revealed last weekend that Carillion needs hundreds of millions of pounds within weeks to survive.
Unless that funding materialises - either from commercial lenders or in the form of emergency Government support - an administration would put at risk the jobs of at least some of the 19,500 people it employs in the UK.
Carillion has a pension deficit of roughly £580m, although this figure would be expected to rise sharply if measured according to the cost of insuring its various retirement schemes on a full buyout basis.
The rescue plan shown to lenders on Wednesday includes handing back some loss-making contracts, revising the terms of others and potentially accepting financial support from the Government if it cannot secure it from private sector sources.
Carillion's large syndicate of lenders includes Barclays, HSBC and Santander UK, as well as a host of overseas firms.
So far, many of the banks have indicated that they are reluctant to provide additional funding given the potential for huge losses on their existing exposure.
Their attitude is said to have prompted senior figures close to Carillion to discuss the possibility of emergency financial support from the Government.
A number of disposals aimed at raising cash, including that of its Canadian operations, are progressing more slowly than originally anticipated.
Its only asset sale since the crisis erupted has been to offload a portfolio of healthcare contracts to rival outsourcer Serco for £50m - against a broader forecast for disposal proceeds of £300m.
If it survives in the short term, Carillion is also working on a plan to swap £1bn or more of its borrowings for new shares in the company, which is one of the Government's most important infrastructure delivery partners.
Such a plan would leave its pension scheme, or the Pension Protection Fund, as a big shareholder.
The Wolverhampton-based group is the second-largest supplier to Network Rail and maintains approximately half of the UK's prisons as well as roughly 50,000 homes for the Ministry of Defence.
It is also engaged in building the Aberdeen Bypass and was responsible for constructing the Tate Modern art gallery in London and the Channel Tunnel.
Last week, the company was dealt a fresh blow when the City watchdog launched a probe into the "timeliness and content" of statements it made to the stock market about is financial position between December 2016 and July last year, when a massive profit warning sent its shares crashing by 75%.
Since then, the company has cleared out its executive team, including chief executive Richard Howson and finance director Zafar Khan.
Mr Howson was replaced on an interim basis by Keith Cochrane, the former Weir Group boss, with Andrew Davies due to arrive from Wates Group as his permanent successor on 22 January.
Carillion reported a first-half pre-tax loss of £1.15bn in September, while it announced just before Christmas that its lenders had agreed to defer a test of its borrowing agreements from 31 December to 30 April.
Carillion and EY declined to comment.