The National Audit Office (NAO), the UK's public spending watchdog, has said it plans to investigate the Lower Thames Crossing, a proposed £11bn road tunnel between Kent and Essex. The move follows sustained pressure from campaigners worried about the rising costs of one of Britain's largest infrastructure projects, and it matters because the scheme is being financed partly through public money to build what will ultimately be a privately run asset. NAO head Gareth Davies wrote to opponents saying he anticipated he would "examine and report" on the project, and that his teams had already begun tracking its progress.

Ministers committed this month to proceed with the long-delayed project after it was spared from billions of pounds in infrastructure cuts made to accommodate a £15bn rise in defence spending. The government has committed £3.1bn to constructing the twin 2.6-mile tunnel, designed to ease congestion at the Dartford Crossing, with the rest expected to come from the private sector; a further £174m of public money emerged last month, and more than £1bn has already been spent before any building begins. A licence to run the new and existing tunnels is due to be handed to a private consortium in 2029, with works scheduled for completion in 2034, while campaigners at the Transport Action Network hope the arrival of Andy Burnham as prime minister could prompt a rethink.