Britain’s great vanity project is hanging by a thread. Reports that the treasury secretary, Liz Truss, has made HS2 a candidate for the autumn’s public spending review have rung alarm bells across Whitehall. The railway was previously thought a done deal; but last month, ministers quietly postponed the HS2 company’s “authority to proceed” with construction contracts by six months, until after the budget. Now Truss has declared her determination to “junk the white elephants”. HS2 is an elephant in a class of its own, as its cost heads from its supposed £56bn towards £80bn to £100bn. It is on its third chief executive and recently lost its chairman, Terry Morgan.

Truss is an outsider for the Tory leadership, or at least to be next chancellor. HS2 is hated by her department and has been sustained only by the past support of David Cameron and Theresa May. Cancellation would make a lot of Tories very happy, and show Truss as a strong and decisive minister, a rarity at present. The project’s sole surviving champion is transport secretary Chris Grayling, now playing a loyal Fool to May’s King Lear. Where will either be come the autumn?

HS2 was a dream of the 2000s. It was only adopted by David Cameron as a bizarre alternative to another Heathrow runway

There are other straws in the wind. Insiders talking to Channel 4’s Dispatches team were virtually agreed it might not proceed beyond Birmingham, undermining its cost-benefit value. Parliament has still not been asked for statutory authority to proceed north of the Midlands. The Treasury’s former chief, Nick Macpherson, has dismissed the whole venture as Cameron’s “political vanity project”.

More serious is the loss of HS2’s most strident backers in the north, now favouring the Northern Powerhouse Rail project, dubbed HS3. Given the dire state of Transpennine rail links – probably the worst commuting services in Britain – Manchester’s mayor, Andy Burnham, had declared west-east “the single highest transport investment priority in the country”. Britain’s rail passenger growth has ceased its recent rise, and forms just 2% of passenger journeys overall.

It is commuter railways, especially in the provinces, that are screaming for investment. The government’s obsession with another London-oriented mega-project is baffling.

HS2 would hardly be the first rail project to be abandoned. A century ago, Edward Watkin’s great scheme to drive a train from Manchester through the centre of London and on to Paris got no further than Marylebone – though he did start digging a Channel tunnel.

The HS2 project has not got that far. Despite delays, it has spent £4bn on “preparatory work”, including £600m on a consultancy gravy train. Site clearance has begun at Birmingham, Old Oak Common in west London, and Euston. Various fallback positions have been in the wind, of which the sanest would be to halt HS2 at Old Oak Common at the junction with London’s delayed Crossrail. This would at least save the exorbitant cost of tunnelling into an already overcrowded Euston.

HS2 would widen UK north-south divide and should be axed, says report Read more

For Truss, cancellation would combine fiscal prudence with serious political gain. Leaders of northern city councils – where the Tories’ plight is currently desperate – backed HS2 because it was the only transport investment in sight. Cancellation would enable Truss to press the go button on HS3, and produce instant ecstasy. She would be feted from the Humber to the Mersey.

HS2 was a dream of the 2000s. It was a rocket to the moon, a gas-guzzling Concorde on wheels. It was only adopted by Cameron as a bizarre alternative to another Heathrow runway, which he pledged not to build. It has been the state’s biggest land acquisition programme since the second world war. Cancellation would release thousands of acres for development, not least in downtown Birmingham. The benighted railway would be freed from the nightmare incubus of an elite train service that is no one’s current priority.

Truss will need courage to stand up to what is now a gold-plated, publicly funded, one-project lobby. But she has a last opportunity to take a brave but sensible decision. All mega-projects are ultimately about politics, where they are soon enmeshed in tribal rivalries. But when, as with HS2, enormous sums of money and disruption to the lives of thousands are at issue, the public has a right to second thoughts. On this as on all things.

• Simon Jenkins is a Guardian columnist