“Out of date and unconvincing” was how a House of Lords report described the evidence the government was using to justify the HS2 railway line.

A damning report from the Lords' Economic Affairs Committee released today said the government had “not made a convincing case for why this particular project should go ahead”.

It also stated businesses in London would benefit most from the new railway line, despite claims from the Department for Transport it will increase economic growth in the north.

The DfT said today it was confident building work on the first section of the line, which will cut through the Chilterns Area of Outstanding Natural Beauty on its way from London to Birmingham, would begin as planned in 2017.

But the report from the House of Lords committee said: “We do not believe that the government has shown that HS2 is the best way of stimulating growth in the country.

“While investment outside London is long overdue, evidence and experience from other countries has suggested that London would be the biggest beneficiary of a project such as HS2.

“The cost-benefit analysis for HS2 relies on evidence that is out-of-date and unconvincing. The government needs to provide fresh, compelling evidence that HS2 will deliver the benefits it claims.

“We welcome the objectives the government has set. We fully support investment in UK rail infrastructure. But the government has not made a convincing case for why this particular project should go ahead. The analysis presented to justify the project is seriously deficient.

“The project has to be developed against a background of financial restraint and it is not at all clear that HS2 represents the best, most cost-effective solution to the problems it is intended to solve.”

It went on: “The scale of the alleged capacity problem is unclear and the government has not demonstrated that HS2 is the most effective way of achieving the desired rebalancing of the economy.

“The government’s principal justification for building HS2 is to provide capacity to meet long-term rail demand.

“Inadequate information on rail usage and demand modelling makes it difficult to determine whether this is correct.

“Overcrowding appears to be caused by commuter traffic, not long-distance traffic, and is exacerbated by inflexible pricing.”

The report concluded: “It is impossible to agree with the government that HS2 is the only solution to increase capacity on the rail network.

“Additional capacity could be provided by incremental improvements to the existing network, a new conventional railway line, or a new high-speed line.

“These options have not been assessed equally, with only HS2 receiving serious consideration by the government.”

A map in the Lords report also makes reference to a possible connection from the HS2 line to Heathrow Airport, but Transport Secretary Patrick McLoughlin said recently in a letter to Beaconsfield MP Dominic Grieve this is a plan that is no longer being considered by the government.

The Department for Transport said in a statement: “The case for HS2 is crystal clear. It will have a transformational effect, supporting growth in the north by improving connectivity, freeing up space on our crowded rail network, promoting regeneration, boosting local skills, generating tens of thousands of jobs and helping secure the UK’s future prosperity.

“We have been fully transparent about the project. HS2 will deliver over £2 of benefits for every £1 invested and the economic benefit of the project was recognised by MPs of all parties who voted 452 to 41 in favour of HS2 at the second reading of the hybrid Bill.

“Demand for long-distance rail travel has doubled in the past 15 years and without HS2 key rail routes connecting London, the Midlands and the North will soon be overwhelmed, stifling growth in towns and cities across the country.

“It is crucial we press ahead with delivering HS2 on time and budget and we remain on track to start construction in 2017.”

The full report can be viewed by clicking here.