Former chancellor Alistair Darling has added his voice to calls urging the Coalition to scrap the High Speed 2 (HS2) rail project.

Writing in The Times today, Mr Darling, who served as transport secretary for four years, says the estimated £50bn costs would be better allocated on schemes that would boost economically lagging English regions.

Mr Darling warned the economic case had become ‘highly contentious’ in light of technological advances. He also said the proposed route neither links with key transport hub the Channel Tunnel route at St Pancras, nor with Paddington, which connects with Heathrow airport.

‘Put it another way,’ Mr Darling states. ‘If you gave England’s biggest cities £10bn each for economic development, would they spend it on HS2?’ he asked.

He suggested the English regions would instead prefer to spend it on smaller scale investment, on housing or transport, and argued it ‘seems foolish’ to commit future governments to a single project whose costs would swallow up increasing sums - ruling out spending on other infrastructure projects.

The former chancellor’s words will cause further consternation among Coalition supporters of the controversial scheme to boost rail capacity, as well as Lord Adonis, who was Labour’s last transport secretary.

Earlier this week, the Institute of Economic Affairs think-tank produced evidence suggesting the final costs of HS2 should be uprated to £80bn – with local authority planning fee charges contributing to the upwardly revised estimate.

Many Conservative MPs, whose Chiltern and Buckinghamshire constituencies would be affected by the proposed route from Euston to Birmingham, are also expected to continue their opposition to HS2.

In addition, a group of councils has banded together to form the ‘51m’ group to contest the evidence base for the economic benefits of the project.

Their cause was given a further boost this week after the Financial Times disclosed the concerns of senior officials from the Treasury worried that financial modelling indicates HS2 costs could spiral to at least £73bn.