The debt-ridden contractor also confirmed it had held talks with it rebel main shareholder, Coltrane Asset Management, about looking at a better deal, but said the only proposal on the table remained the plan that left all existing shareholders with 5% of the business.

Interserve issued a statement yesterday evening after reports that it may sweeten the present debt for equity swap plan for a second time to leave shareholders with a 7.5% interest in the group.

But the board quashed rumours about a last-ditch deal sweetener to win over Coltrane.

The stage is now set for a nail-biting few days ahead of Friday morning’s crucial rescue plan vote.

Interserve has warned that should it fail to gain shareholder approval, lenders would instantly place the group into a pre-pack administration, leaving shareholders with nothing.

The firm said the new pre-packed firm would continue to trade saving jobs and pensions, although there were no reassurances about where trade contractors and suppliers would stand.

In ever more challenging exchanges, majority investor Coltrane has threatened to hold Interserve bosses personally liable for millions of pounds of losses should the firm fall into administration.

It is understood to have written to directors to warn them that it will take legal action for what it claims are disclosure failings and unfairly favouring lenders over shareholders.

In the statement issued last night, Interserve said: “The board confirms that it has been in discussions with Coltrane and its lenders which have sought to establish the basis on which Coltrane would support the company’s restructuring proposal.

“Although the board is seeking to improve the position of all shareholders, there is no certainty that it will be able to do so in the very limited time available.

“The only proposal which is currently capable of being implemented is the recommended Deleveraging Plan through which, inter alia, shareholders will retain 5% of the equity of the restructured Interserve with the ability to acquire further equity through the open offer.”