Angry councillors in north London have called for a "forensic audit" of the proposed budgets for the controversial High Speed 2 (HS2) railway.
Camden Council believes the compensation package being offered by the government is inadequate.
The authorities have set aside £400 million to counterbalance the disruption that the construction process is likely to cause in the area. However, an independent report has now found that the actual sum required could top £1 billion.
According to analysis by Lambert Smith Hampton, Regeneris and Pell Frischmann, the government's £1.3 billion compensation budget for the entire line between London and Birmingham may be a significant underestimation.
Network Rail recently said HS2 has the potential to benefit transport networks in more than 100 UK towns and cities, but Camden Council leader Sarah Hayward is far from sure that the project is viable.
"Time and time again doubt is cast on the business case put forward, the budget and the overall need for HS2," she remarked.