Chester Farm total cost expected to be £11m
Taxpayers are to underwrite a potential £2.2m shortfall in plans to open a fire-damaged Grade II listed farmhouse to the public, it has emerged.
In July, the Heritage Lottery Fund pledged £4m to the opening of Chester Farm, in Irchester, where human activity dates back 10,000 years.
Northamptonshire County Council has already set aside £4.9m to help meet the expected £11m project cost.
On Tuesday, the council's cabinet will be updated on the Chester Farm plan.
A report to the cabinet, which outlines the business plan, said a conference centre planned as part of the project would help the complex become self-financing.
It states part of the overall cost includes £2.2m of "unsecured funding" from "other sources".
The report said: "However this cannot be guaranteed and, depending on the actual funding secured through this source, the council will need to underwrite any potential shortfalls from the assumed £2.2m to enable the plan to be delivered. underwrite any potential shortfalls from the assumed £2.2m."
The house, which was built near the site of a walled Roman town, was severely damaged by a fire in 2010.
The council received a £1.9m insurance pay-out to repair the 17th Century building.
County council leader Jim Harker said the property was a "site of national importance".
The 45-acre (18 hectare) property was bought by the council in 2004 after it became uneconomic as a farm unit.
The site includes an Iron Age settlement, a complete Roman town and the deserted medieval village Chester-by-the-Water.
The council hopes the first phase of the development will be open to the public within two years.