Rarely has a debate sparked such vitriol and bitterness as the question of whether the United Kingdom should build a high speed rail line.

The level of animosity was highlighted by the Transport Select Committee, as MPs complained that supporters of the planned line, even including the former Transport Secretary, had condemned opponents as “nimbys”.

MPs also criticised opponents of high speed rail for touring the country with an inflatable white elephant. Although this wasn’t a personal attack on the other side, it was still a rather childish way of making a point about a serious topic, the Committee said.

But perhaps disagreements about the high speed line, known as HS2, even proved too much for the Select Committee itself.

Because the long-awaited report, published like all Commons committee documents on behalf of the entire House of Commons, sends out distinctly mixed messages.

It concludes by backing the HS2 scheme, but the support is shrouded within so many caveats that it’s barely worthy of the name.

Tucked away in one paragraph is a demand that a final decision on the first phase, from London to Birmingham, should not be made until details of the second phase have been published and a consultation carried out.

As a firm decision on the first phase is expected before Christmas, this is clearly impossible without delaying the plans.

Then there is criticism of the Government’s decision to build the line running through the Chilterns instead of following existing transport routes.

But MPs also make it clear that the alternative route is impossible unless trains are limited to speeds of around 150mph, instead of the 250 mph planned. Faster trains need shallower bends, so there is far less flexibility about where the track can be laid.