The review, launched by the prime minister in the summer, found that without the extra capacity the new line would bring to relieve overcrowded services, “large ticket prices” would be needed to discourage people from travelling at peak times.
A leaked version of the report, which is not set to be released officially until after the general election, was obtained by The Times.
The leak will pile pressure on Mr Johnson to clarify his policy on the line, which runs through his constituency, before next month’s vote. The prime minister has previously criticised the project, but stopped short of saying he would scrap it. Labour supports the line in principle and included an extension to Scotland in its 2017 election manifesto, although it has criticised rising costs.
The review’s authors note that cities in the north and the Midlands, even those not directly served by the line, will benefit from improved local and regional services thanks to the capacity that is freed up.
Douglas Oakervee, the former HS2 chairman appointed by Mr Johnson to lead the review, says in the leaked draft that the journey time from Leeds to Birmingham would be more than halved, and an hour cut from the journey between Newcastle and Birmingham.
The review proposes only relatively minor changes to the project, and dismisses plans to halt the project at Old Oak Common on the outskirts of London or reduce its operating speed as not viable or desirable.
However, it admits that the project’s costs have continued to rise and that it may end up costing more than the new £88bn price tag, citing failures in the project’s procurement strategy. Taxpayers would still gain between £1.30 and £1.50 benefit for every pound spent on the project – although this is down from the £2.30 estimate at the original costing.
One suggestion the draft report makes is to reduce the planned number of trains operating on the line each hour from 18 to 14, in line with other high-speed networks around the world, according to the BBC.
It also says there are no “shovel ready” alternatives to the plan that could provide the same scale of benefits.
HS2 will from travel from London to Birmingham, and then split into a Y section to carry trains onwards to the East Midlands and Leeds in the east, and Manchester in the west.
Many services will be operated with so-called “classic compatible” trains, meaning they will be able to run on existing lines, but benefit from the new line’s speed and capacity. Such services will serve cities like Newcastle, Liverpool, Glasgow, Sheffield and Edinburgh; as well as other destinations like Stoke, Stafford, Macclesfield, Warrington, Wigan, Preston, York, Darlington, and Chesterfield.
Additionally, the government’s strategic case for HS2 envisages more regional and stopping services to destinations on existing lines using the capacity freed up by shifting fast inter-city services to HS2.
Henri Murison, director of the Northern Powerhouse Partnership, said: “The Northern Powerhouse Independent Review on HS2 said that there were no identified credible alternatives to HS2 in order to deliver the same capacity, and that it has the potential to unlock greater growth in the north and Midlands. It is welcome that their recommendations are mirrored by the government’s own Oakervee Review.”
But Penny Gaines, chair of the Stop HS2 campaign group, said: “HS2 was a bad project when it was originally announced and was supposed to cost £33bn, it was a bad project when it was supposed to cost £55bn and it is a bad project now the cost is expected to be more than £88bn. It should be cancelled as soon as possible, so the government can focus on the real transport priorities.”
The government says the report hasn’t been finalised, and that the Department for Transport has not been given a copy.