Parliament has been seriously misled by “fiddled” figures about the true cost of HS2, according to the deputy chairman of a review into the project.

In November, Lord Berkeley demanded his name be removed from the review, commissioned by the government, after a leak of its conclusions suggested the line should be built in full.

He has now published his own dissenting assessment, claiming the cost of the line is “completely out of control”. It also concludes HS2 would not benefit the north and the Midlands as ministers have promised.

Speaking to Sky News, Berkeley said the directors of HS2 had “fiddled the figures” to overstate the benefits of the project and minimise the costs. He said the project assumes 18 trains will run on the line every hour, four more than is allowed on high-speed lines in other parts of the world. “The revenue [assumption] is all shot to pieces,” Berkeley said.

He said he wrote his report because he disagreed with, and was not given the chance to amend, some conclusions of the draft report overseen by Doug Oakervee, the former HS2 Ltd chair appointed by Boris Johnson to lead the review into “whether and how we should proceed” with the project. Oakervee’s official report has yet to be published.

Berkeley’s report says: “HS2 Ltd has designed the scheme for 360-400km/h (223-248mph), higher than any other high-speed line in Europe or Japan, and for 18 trains an hour in each direction, when the company itself admits that no other such high-speed line is able to run more than 12 to 14.”

Berkeley, a former Labour transport spokesman who was named as deputy chair of the Oakervee review by ministers as proof it would be balanced, said the government knew about the ballooning costs up to four years ago.

The line was initially expected to cost £50.1bn. Latest estimates by HS2 Ltd – the private company in charge of the project – put the price at £88bn. But Berkeley says independent analysis arrives at a figure of at least £107.92bn.

“I believe that parliament has been seriously misled by the failure of HS2 Ltd and by ministers to report objectively and fairly on costs and programme changes,” Berkeley writes in his report.

Berkeley says information disclosed to the review panel raises “very serious concerns about the competence of HM Treasury and the Department for Transport (DfT)” in relation to the project, and that of HS2 Ltd.

He told Sky: “The costs were clearly known to the Department for Transport, and I believe ministers, three or four years ago.”

In his report, Berkeley says he wrote to Oakervee to detail his concerns about the review. These included “a bias towards accepting HS2’s evidence in preference to those of others, leading to what I considered to be a critical but supportive recommendation for HS2 Ltd to continue. I do not believe that the evidence that the review received supports this view.”

Berkeley said that while economic modelling by HS2 Ltd had arrived at a conclusion that the benefits of the project would be more than twice its costs, his best estimate was of a benefits-to-costs ratio of less than one, and possibly as low as 0.6, making it “poor value for money”.

He also said plans to build HS2, compared with improving existing lines, were not good for the environment.

Berkeley added: “The real problem is that railways in the regions, in particular the north and the Midlands, are really bad and it is them that need investment for local commuters.

“Getting to London is secondary for most people except for MPs and the managing directors of companies. So attracting business to these areas will be done by improving the commuter services dramatically to make them look more like London services, which are on the whole very good.”

Berkeley’s report was welcomed by anti-HS2 campaigners and environmental groups. Penny Gaines, the chair of Stop HS2, said: “It is time for this white elephant of a project to be cancelled as quickly as possible.”

Six environment groups, including Greenpeace, Friends of the Earth and the Royal Society for the Protection of Birds, issued a joint statement expressing alarm at how the Oakervee review had been conducted.

It called on the government to “scrap – or at least significantly recast – the HS2 project, particularly given its many damaging environmental impacts and the better alternatives to improve our train network”.

Phase one of HS2 is planned to run between London and Birmingham. It was initially scheduled to launch in 2026, but a recent report by HS2 Ltd stated this could be pushed back until 2031.

A HS2 Ltd spokesman said: “There have been many individual views expressed about the HS2 project. However, we await the publication of the government’s official review.”

A DfT spokesman said: “The government commissioned the Oakervee review to provide advice on how and whether to proceed with HS2, with an independent panel representing a range of viewpoints. Lord Berkeley‘s report represents his personal view.”