Fire engines and kits used by London Fire Brigade could be "put up for sale to settle the debts" of the firm which contracts them out, a union has said.
AssetCo, which provides and maintains equipment for London Fire Brigade (LFB), is facing a creditor's petition from Northern Bank over a £1.3m debt.
The Fire Brigades Union said LFB faced a "serious crisis" as the stock could potentially be sold to recover money.
LFB said it would not speculate but planned for "all events".
Under a private finance initiative AssetCo provides and maintains fire engines and equipment for LFB.
It is understood that in the event of non-repayment of debt the stock could be sold off or a new buyer for the contract with LFB would be sought.
Failing these, an offer could be made to LFB to buy out the entire contract or parts of it.
The BBC understands the LFB could consider such an offer but would prefer another supplier to come forward.
Ben Sprung, London FBU regional organiser, said: "We could end up with all London's fire engines and kit being put up for sale to settle the debts.
"It is a scandal that the ownership and maintenance of critical equipment is in the hands of a company which has reached this state.
"The fire authority need to set out what it has done and what fall-back plans it has. The mayor needs to get a grip on this before it's too late."
LFB said it would not be left without fire engines. A spokesman said: "We plan for all events that could affect the fire and rescue service we provide."
In a statement on its website AssetCo said the company was in "constructive discussions", adding: "Northern Bank based in Belfast, Northern Ireland, has lodged a creditors' petition in respect of its debt of £1.3m owed by the holding company.
"This effectively seeks to improve the bank's position, and the position of its guarantor, ahead of other banks and creditors, and if not settled the petition will be heard on 29 June 2011."