02/09/2013 10:35 BST | Updated 02/11/2013 05:12 GMT

HS2: U-turn If You Want to, the Train Is Not for Turning

As public and parliamentary support for HS2 falls, surely it is only a matter of time before one of the parties changes their position. At the rate things are going, the debate may well descend into a race to see who will be the one to push the plans well and truly off the rails.

It has been branded as the future of transport in Britain, but High Speed 2 could be about to be derailed. With Britain lagging behind the continent in its development of modern rail links and with the country in desperate need of improved rail capacity, the three major parties are nominally united in their support for HS2. However, recent changes in public opinion and backbench dissent have meant this consensus could be beginning to crumble.

Labour's commitment to the project seems to be faltering; while Ed Miliband remains in favour of it, Peter Mandelson and Alistair Darling, two party heavyweights and former HS2 advocates, have turned their backs on the project, with the former calling it "an expensive mistake" and the latter, "a nightmare". Ed Balls is qualifying his support: vague threats that there would be no "blank cheque from a Labour Treasury for HS2" seem to suggest his purse strings will not be stretched much further than the latest estimate's £42.6billion. Meanwhile influential Conservative voices such as Lord Ashcroft's have been urging the government to rethink its position before Labour gets there first.

In a project where costs are so high, it is vital that there is a clear end-goal in mind. Obviously it is to get people from A to B faster, but to what end? In the case of HS2, many northern constituencies feel the plans with only serve to further inflate London's sense of importance and drain talent from regions which are increasingly within commuting distance of the capital. Such a London-centric approach is arguably not the most effective way to improve the railways, as it is already easy to travel the length of the country at some speed, leading to suggestions that the money could be better invested in cross-country routes.

The benefits to London are no more assured. The excess passengers would certainly take their toll on London's already stretched underground network and TfL boss Mike Brown made a strong case that Crossrail 2 is absolutely necessary to take the heat off. Boris has been playing his part in encouraging the government to rethink its plans, predicting that costs are likely to spiral to £70billion or more. This estimate does not seem wildly unlikely; as the Said Business School at Oxford University has recently demonstrated, the incidence of underestimates is higher in rail developments than any other large-scale infrastructure projects.

Ed Miliband maintains the claim that HS2 will have major economic benefits to the cities it links. Whist this remains uncertain it may have the adverse side effect of having a negative effect on those it does not reach. Coventry has only recently decided to neutralise its staunch opposition to the project, but fears remain that the city will lose out. HS2 Limited estimates the current three Virgin trains per hour from London to Coventry will have to be reduced to two. Restricted access to the city and the choice of Birmingham rather than Coventry as the Interchange station has led to worries that regional investment will be focused in Birmingham rather than Coventry's already flagging city centre.

However, a boost to the regions is not necessarily the desired effect of HS2 (or at least not its sole purpose). Shadow Transport Minister Maria Miller has argued that HS2 is the only reasonable proposal to address the issues of capacity. Perhaps, therefore, the value of HS2 comes not in a wider transformative effect, but just an improvement of the status quo. Indeed, Lord Adonis has claimed that an upgrade of the London - Birmingham alone line would cost £20billion and would have only two thirds of the capacity of HS2.

According to this week's statement from the Institute of Directors (IoD), HS2 will not live up to expectations of reducing business costs lost to time spent on trains. HS2's analysis was conducted in a pre-tablet world, when many of us still read a good novel on the train or gazed dreamily out the window at the rolling countryside. Now, you are more likely to see business travellers making themselves useful on their laptops and tablets as Steve Walker, the Director General at the IoD, has claimed that the majority of their members reported that their productivity levels were no lower on the train than in the office.

The doubt surrounding HS2 appears to be catching, as more and more politicians speak out against it: in the first YouGov poll conducted after Mandelson's pull-out, public support had dropped seven points to 34% and opposition was up three points to 46%.

As Matthew Elliott from the TaxPayers' Alliance suggests, this could be an important opportunity for Miliband. "Labour needs to match the overall Tory spending envelope but find other ways of offering some differentiation. The most readily available pot of cash is in the big, expensive infrastructure projects. Of these the one with the biggest outlay and most flaky financial grounding is high-speed rail." However, Ed Miliband can be forgiven for wanting to play it safe at the moment: Labour can't be seen to be backtracking on an economic plan rooted in major capital investment and will need to come up with some better ideas of their own to properly demonstrate their commitment to efficient investment.

It might be shrewd for Cameron to capitalise on this hesitancy while he can and swallow the bitter pill of short term humiliation to avoid greater criticism later. With dissent coming from the backbenches and true-blue strongholds in Buckinghamshire and key marginals in the Midlands and North, HS2 is perhaps proving more trouble than it's worth. Cameron was clearly willing to handle some discontent in the South in his initial support for HS2, but given that it has garnered little enthusiasm in the North, the potential payoff seems to be on rocky ground. Given the danger posed by UKIP in the run-up to the general election, and the fact that Farage's candidates in the South will be campaigning hard against HS2, it may be unwise to take such a risk.

In the run up to the general election, HS2 perhaps seems to hold little sway with voters, left or right, north or south. At best it is greeted with apathy and at worst, it may turn some key constituencies away from Cameron. But as public and parliamentary support for HS2 falls, surely it is only a matter of time before one of the parties changes their position. At the rate things are going, the debate may well descend into a race to see who will be the one to push the plans well and truly off the rails.

An earlier version of this piece originally appeared in the Weber Shandwick Knowledgeshop