It would be “crazy” not to reassess whether the full HS2 rail project remains viable, Grant Shapps has said, amid signs the government could axe the northern leg. After nearly a week of briefings that ministers are preparing to ditch the Birmingham to Manchester section, the defence secretary refused to rule out such a move. Instead, he said Covid, the war in Ukraine and inflation had severely affected public finances. “It would be irresponsible to simply spend the money – carry on as if nothing had changed – if there has been a change in that fiscal picture,” Shapps told the BBC. Shapps, who was transport secretary until last month, said a responsible government should ask: “Does this still stack up for what the country requires, in terms of where it’s spending its resources, and at what time?” Rishi Sunak, the prime minister, is expected to hold a meeting the chancellor, Jeremy Hunt, in the coming days, with sources telling the Observer they would aim to make a decision by the middle of next week. It is hoped an announcement will be made before Conservative party conference begins in Manchester next Sunday. Some Tories have argued HS2’s spiralling costs means it should be trimmed, or the timetable for its full delivery pushed back. An initial cost of £33bn in 2010 has since soared to £71bn and is now feared to be closer to £100bn. Shapps stressed no final decision had been made about the future of HS2. But he said: “Any government that doesn’t go back and look at it is crazy.” Shapps also told Sky News: “If you don’t stop and reflect after things have changed, that is a foolish approach.” Though there has been pushback from former prime ministers David Cameron and Boris Johnson, as well as Andy Street, the Conservative mayor of the West Midlands, Shapps said that was “rather jumping the gun because no decision has been made”. Labour resisted committing to deliver the project in full under its existing timetable. Darren Jones, shadow chief secretary to the Treasury, stressed “we would like to see HS2 built in full” but said he would not “announce policy on TV shows on the basis of rumours and leaks”. He told the BBC: “We don’t know what the cost overrun is. We don’t know which bits of the projects are costing how much extra money. We don’t even know what the Conservatives in government are going to do about connections or endings or extensions. We can’t answer questions until they do so.” However, Andy Burnham, the Labour mayor of Greater Manchester, was less equivocal. Asked on Sky News whether Labour should commit to building HS2 from central London to Manchester, Burnham said: “I have been saying that to them. “I said it yesterday, I will say it again today: the north of England should not be forced to choose between whether we have a good east-west line or a good north-south line.” Speaking on the launch day of the new Bee network, which will see buses brought back into public control as part of a new integrated public transport system, Burnham added people were “fed up with false promises”. He hit out at “the desperate acts of a dying government” over HS2 but said he awaited confirmation about the future of the Birmingham to Manchester leg.