HS2 is over budget and behind schedule because the complexity and risks of the project were under-estimated, according to a report by the National Audit Office (NAO).
The watchdog for Whitehall spending warned that despite various projections and promises, it is impossible to “estimate with certainty what the final cost could be”.
The high speed rail project was allotted £56 billion in 2015, but the government-commissioned Oakervee review leaked earlier this week predicted the bill could reach £106 billion.
The NAO has now urged the government and HS2 Ltd to be “transparent and provide realistic assessments” in relation to the project.
The aim is to improve connections from London to Birmingham and Manchester with a new high speed network.
The first phase between London and Birmingham was meant to kick off in 2026 but is now forecast to start between 2031 and 2036.
Head of the NAO Gareth Davies said the issues with the project provided “important lessons” for the Department for Transport and other major infrastructure programmes.
He said: “To ensure public trust, the Department and HS2 Ltd must be transparent and provide realistic assessments of costs and completion dates as the programme develops, recognising the many risks to the successful delivery of the railway that remain.”
But whatever the cost, Richard Houghton from HS2 Action Alliance said the plans have “never been worth the money”.
The group looks at the business case surrounding the proposals – Mr Houghton said HS2 is “exactly the wrong project in the wrong place at the wrong time”.
Environmentalists including Extinction Rebellion and the Wildlife Trust have also voiced their opposition, saying it would destroy dozens of “irreplaceable” ancient woodlands.
However, some argue the reduced journey times and better connectivity will bring economic benefits to parts of the country.
Transport Secretary Grant Shapps said the fate of the plans will be decided by “in weeks rather than months”.
talkRADIO: Listen live