By Daniel Hunter

The £15bn Crossrail project is “on course” to be completed value for money, according to the National Audit Office (NAO).

The project, which is half-completed, will see 26 miles of new tunnels constructed under London and link the capital to the South East of England.

NAO chief Amyas Morse said: “The sponsors and Crossrail Limited have so far done well to protect taxpayers’ interests, by taking early action to stop costs escalating and, during construction, tightly managing the programme.”

The NAO did admit that there have been additional costs, such as an extra £1bn used to purchase trains.

The NAO’s report into the project also found that the Department for Transport (DfT) has not received as much private investment as it was hoping for.

The project was due to be a public and private sector joint venture with Transport for London (TfL), who are footing the majority of the bill, Department for Transport, Heathrow Airport and private businesses contributing to the cost.

Private businesses are contributing to the cost through a supplement of business rates in London. But the NAO says not as many businesses are contributed as was expected.

The Civil Aviation Authority (CAA) also recommended that Heathrow Airport contribute a significant amount less than was originally planned. It was expected that Heathrow would contribute £230m to the project as it would “benefit”. But the CAA said there wouldn’t be a net benefit, and the airport should contribute just £70m to the Crossrail project.