Uninsured Loss Recovery providers outside the Association of British Insurers' agreement on credit hire rates could reap an estimated £100m windfall if Helphire wins a credit hire case this autumn.

The case is being brought to clear up confusion left unresolved after the landmark House of Lords judgment in Dimond v Lovell court case in May, which decided credit hire agreements are only enforceable if they conformed to the Consumer Credit Act.

Helphire, whose previous policies did not conform to the Act, has written to the head of the civil courts division, the Rt Hon Sir Richard Scott, asking to clarify the vague definition of the daily “spot rate” for the recovery of replacement car costs.

It hopes the case will help unlock £82m worth of debt from 20,000 credit hire cases it has that are currently bogged down in the courts system.

Another non-ABI agreement credit hirer, Accident Assist a subsidiary of GE Financial Insurance, said it has 115 cases under negotiation.

A senior source in the credit hire industry said insurers are taking an increasingly hard line on non-ABI agreement credit hirers.

He said one insurer has built up a “fighting fund”of £5m to contest non-ABI agreement credit hire cases and knew other insurers likely to follow.

Peter Holding, Helphire legal director, said a definitive ruling would benefit both insurers and credit hirers.

He said: “The Court of Appeal is seeking to select a sample of cases that reflect the legal principles involved in our block of cases and we hope, deliver a definitive ruling that will allow the remaining cases to be settled quickly.”

The legal move follows Helphire's annual meeting last week, at which chairman Martin Kinney said its volume of unsettled cases has led to increased administration costs and interest charges for the company.

He also warned that Helphire may be unable to match its pre-tax profits of £6m last year. It has already sold £2.75m worth of shares in internet company Freeserve to ensure an “exceptional” profit in the coming year.

Holding stressed that Helphire does not resort to legal action against insurers lightly. It offers insurers a 10% discount if they settle cases within 28 days.

A Lord Chancellor's Department spokesman confirmed Sir Richard Scott has agreed to bundle together Helphire's outstanding credit hire cases.

But he added that he had yet to decide how the court would deal with the cases or set a hearing date.