Britain’s biggest HS2 contractors have launched an 11th-hour effort to convince Rishi Sunak not to cancel the high-speed rail line to Manchester, pledging to find cost savings and private investment to make the scheme feasible. On a day of renewed chaos for the government over the rail line’s future, Andy Street, the Conservative mayor of the West Midlands, told the prime minister he was working hard to secure support from the companies involved to slash costs. The businesses include the engineering companies Arup, Siemens and Mace – which collectively employ more than 10,000 workers on HS2 – and were on Tuesday night scrambling to take other plans to the prime minister. Sunak held an emergency cabinet meeting at the Conservative party conference in Manchester on Tuesday and is widely expected to use his keynote speech on Wednesday to confirm plans to drastically scale back the multibillion-pound project. The prime minister has been embroiled in a bitter row with regional politicians, the transport industry and members of his own party amid growing speculation that the line between Birmingham and Manchester and the final section of the route through central London to Euston station were at risk. One plan being considered would involve HS2 trains running on existing tracks between Birmingham and Manchester, Sky News reported on Tuesday evening. This would allow passengers to travel from London on one train, but only at high speeds for the first leg. Sunak refused to confirm whether the line would go ahead as planned after overnight reports suggesting he was poised to announce the cancellation of the northern leg, telling the BBC on Tuesday morning that he would not be “forced into a premature decision”. Arup is understood to be leading the group of companies backing Street’s proposal to find a way to rescue the second phase of HS2. Others include the Manchester-based property company Bruntwood, the accountancy and consulting firm EY and the engineering consultancy Arcadis. The businesses are offering to review the project with the aim of identifying cost-saving measures and ways to increase private investment in the scheme, in a plan that could be taken forward before next month’s autumn statement from the chancellor, Jeremy Hunt. Chris Oglesby, the chief executive of Bruntwood – which is investing hundreds of millions in Birmingham and Manchester and other regional cities of the uk, said scrapping HS2 north of Birmingham would be a “catastrophic decision” and could lead to a huge hike in fares. One senior business figure said the mood among company bosses was far from optimistic after Sunak had made a string of other policy changes in recent weeks that have been poorly received by industry leaders, including watering down the government’s net zero commitments. “It is certainly no way to deliver such a complex major infrastructure project. Given the confusion, a small amount of time out to get into these discussions more seriously, would be most helpful,” the source said. Sunak has appeared to lay the ground for cancelling a large part of the project on the basis of cost, telling Times Radio: “The sums involved are enormous and it’s right that the prime minister takes proper care over it.” However, the businesses involved in the scheme believe there could be several ways to find savings if given the time, including options to adapt the current route, reduce the speeds for sections of the line, and changes to the way that HS2 connects with existing routes and stations. The review would seek to preserve the core of the line from London Euston to Manchester Piccadilly, while existing work already in progress at Old Oak Common and Birmingham Curzon Street would also be continued. A source close to the conversations between business leaders said there was “real effort” to help the prime minister get the support he needed from the private sector to keep the project on track and achieved in a cost effective way. “The private sector are willing to step up to the plate. There are other ways to keep this vital project alive.” Some of the most vocal criticism over the potential downgrading of HS2 has come from Street, one of the Tories’ most senior figures outside Westminster, who told reporters on Monday the prime minister was in danger of “cancelling the future”. The Tory mayor of the West Midlands said on Tuesday he had spoken with Sunak about HS2, telling the BBC that a number of private sector companies were willing to come together to complete the project. “We’ve worked very hard in the last few days to bring forward organisations that have done this elsewhere,” he said. “The prime minister and I spoke last week about the difficulty, and I understand his difficulty and I said I would help him find a solution.”