A former Tory cabinet minister has vowed to oppose government tax rises unless HS2 is scrapped.
Esther McVey dubbed the rail scheme an "unnecessary vanity project" as she pledged to break ranks over the Autumn statement.
Ms McVey, who served as Secretary of State for Work and Pensions between 2015 and 2018, told the Commons that if the government has enough cash for HS2, it should not need to raise taxes.
It comes after Chancellor Jeremy Hunt - who will outline the government's financial plans tomorrow - admitted that taxes will have to go up to deal with the dire state of the economy.
It comes amid calls to scrap the high speed rail project, which critics believe could now cost a massive £155.5 billion due to rising inflation.
Questioning Deputy Prime Minister Dominic Raab, who was standing in for Rishi Sunak at PMQs today, Ms McVey called on the government to rule out tax increases if HS2 is not ditched.
She fumed: "Given that we have the highest burden of taxation in living memory, it is clear that the Government's financial difficulties are caused by overspending and not due to under taxing.
"Does the Deputy Prime Minister therefore agree if the Government has got enough money to proceed with HS2 at any cost, then it has sufficient money not to increase taxes?
"If however, it has so little money it has to increase taxes, which is a last thing for a Conservative government to do, then it doesn't have sufficient money for HS2?
"So can I gently urge the Deputy Prime Minister not to ask Conservative MPs to support any tax rises unless and until this unnecessary vanity project is scrapped? Because I, for one, won't support them."
Mr Raab responded: "I understand her opposition to HS2. I think we have got some very difficult decisions to make, they will inevitably involve a balanced approach, I will leave it to the Chancellor to set them out in the autumn statement tomorrow."
It comes after Mr Hunt told Sky News on Sunday: "We're all going to be paying a bit more tax, I'm afraid."
The first phase of the rail project - linking London with the West Midlands, was estimated to cost up to £45billion, while phase 2a, which would continue the line to Crewe, would cost a further £5.2billion to £7.2billion.
A third section, linking HS2 to Manchester and Leeds, has not been officially costed, but project critic Lord Berkeley estimates the overall cost will now be £155.52billion due to inflation.
He previously wrote to PM Rishi Sunak, The Telegraph reported, saying: “Clearly the Government cannot sit back and watch HS2 bleed the country’s finances dry.”
“Put HS2 into administration and stop all further work, and task the city regions in the North and Midlands to devise a cost-effective and affordable set of solutions to improving their rail connectivity.”
Earlier today Mr Raab bowed to pressure and asked for a full investigation into bullying claims against himself - after two formal complaints were made over his conduct.
The slippery Deputy Prime Minister wrote to his boss Rishi Sunak to ask for an independent probe “as soon as possible”.
He revealed there have now been two formal complaints made against him, after No10 previously said it was not aware of any.
He added: “I will co-operate fully and respect whatever outcome you decide”.
Rishi Sunak confirmed an investigation will take place, replying: "It is right that these matters are investigated fully."
