Has the Government's failure to buy new trains for Thameslink put the entire upgrade of the multi-billion pound route at risk?
The Government was supposed to sign a contract for the trains three years ago.
Today the National Audit Office condemned that delay, saying it could mean the vital improvements to the route delay wont be ready by the deadline of 2018.
Political Correspondent Simon Harris reports.
Delays in awarding the contract to build the trains for the Government's Thameslink upgrade may have put the project in jeopardy, a public spending watchdog says.
The National Audit Office (NAO) says the delays cast doubt on the government's ability to deliver a major upgrade of the key rail route by the 2018 deadline.
– Amyas Morse, Head of National Audit Office
"It's too early in the Thameslink programme to conclude on whether or not it will achieve value for money. That will have to wait until the new service is running. However, there has been good progress in delivering the first stage of the infrastructure part of the programme on time and under budget, which the department now needs to build on. Our principal concern is around the delay in agreeing the contract to build new trains which raises questions about the feasibility of delivering the whole programme by 2018."
A public spending watchdog has cast doubt on the Government's ability to deliver a major upgrade to a key rail route by the 2018 deadline.
Delays in awarding the contract to build new trains for the Thameslink risk putting the entire project behind schedule.
The problems call into question the ability of civil servants to plan complex transport schemes, according to the National Audit Office.
The NAO report found there continues to be a "robust" case for investment in the route because Thameslink is one of the capital's most overcrowded services.
A contract for the trains was supposed to have been signed off by March 2010 but the DfT only selected its preferred bidder - a consortium led by Germany's Siemens at the expense of Bombardier Transportation, which builds trains in Derby - in June 2011 and the deal has yet to be finalised.