Delays in linking up the HS2 and Euston station could mean extra costs and potentially even higher spending.
A near-50 page report by the National Audit Office has found that by the end of December costs for the project had racked up to more than 2-billion pounds.
The planned HS2 route in Buckinghamshire and Oxfordshire will travel through the Chalfonts, Central Chilterns, to the south-west of Aylesbury and across north-east Oxfordshire.
The government insists it's committed to delivering the line and in a way that works out best for taxpayers.
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