Darent Valley Hospital was built under Britain's first PFI deal

Financial hit squads are going into two Kent hospital trusts struggling to balance the books.

Government lawyers and auditors are being drafted into Dartford and Gravesham as well as Maidstone and Tunbridge Wells NHS Trusts in a bid to turn around their finances.

They are among seven NHS trusts struggling to repay controversial private finance initiative contracts.

The deals - similar to a mortgage - involved private firms building and maintaining hospitals, with money repaid over decades.

However, only 8% of PFI deals worth more than £79 billion across the NHS had been repaid two years ago.

Now Department of Health officials have identified £1.5 billion of savings that can be made across the NHS.

The hit squad of experts is being sent into the most-troubled hospitals in an attempt to renegotiate contracts before finances become unsustainable.

The Tunbridge Wells Hospital at Penbury was built under PFI

Darent Valley Hospital, run by Dartford and Gravesham NHS Trust, was built in Dartford in 1997 under Britain's first PFI deal.

However, the hospital has struggled with repayments. Last year, it spent £25 million - 16% of its income - paying back stakeholders.

Maidstone and Tunbridge Wells NHS Trust signed a PFI deal under which private contractor Laing O'Rourke built the Tunbridge Wells Hospital at Pembury and owns it for 30 years.

The trust must pay back the money, plus interest and inflation. It pays £1.7 million a month in repayments, from a monthly budget of £30 million.

Over the 30 years, the total bill will hit £612m - compared to the £228 million paid to build it.

The hospital trusts that need rescuing are: Dartford and Gravesham; Maidstone and Tunbridge Wells; Barking, Havering and Redbridge; North Cumbria; Peterborough and Stamford Hospitals; and St Helens and Knowsley NHS Trust.

A Department of Health spokesman said: "We will be taking action to help trusts save money on their PFI contracts.

"A small team of experts will be going into seven trusts most in need of help in the autumn to identify where savings can be made."

Last year, health secretary Andrew Lansley announced a £1.5bn bailout fund for hospitals struggling to repay PFI deals.

Dartford and Gravesham NHS Trust spokesman said its finances are "sound".

A spokesman said: "The trust has met its financial responsibility to break even for the past five years and it is again on target to finish this year with a surplus. The hospital is performing well and is continuing to deliver first class care to an increasing number of patients.

"The PFI agreement does form a large part of the trust’s financial commitments and we are continuing to work closely with our PFI partners to ensure that the hospital environment is of the highest standard. Two of the leading accountancy firms recently reviewed the PFI contract and we are now working on their findings.

"We welcome any additional help that the team from the Department of Health can offer and look forward to working with them in the autumn. The team of experts will be focusing on our existing PFI contract to verify that we are getting the best possible value for money and that we are fully realising the benefits from the agreement."