The Stone MP, who is a vehement opponent of HS2, said it was 'a disaster for Staffordshire and of no benefit to the country', as he urged Mrs May to scrap the project 'as a matter of urgency'.
It comes after it was revealed that more than £1.4 billion had been spent on the rail link before a single piece of track has been laid.
Accounts set to be published this week are expected to show that expenditure rose by a third last year – fuelling fears that the project will bust its £56 billion budget.
The outlay includes the national headquarters in Birmingham where rent alone is put at £2.8 million a year.
The figures are also likely to include hefty consultancy fees and salaries, including the £750,000 annual pay packet of chief executive Simon Kirby.
Mr Cash, who voted against the HS2 bill in the Commons, said: "All of the most recent figures and reports are pointing in one direction.
"They demonstrate that HS2 is a white elephant that this country can't afford. The figures have never added up and I have argued for as long as I can remember that you can at least double the £56bn they quote."
Mr Cash said Mrs May should scrap the project immediately as she has 'other far more pressing issues to contend with'.
"In the context of Brexit is is a matter of prioritising what we need to do," he said. "The amount of time and money that we would need to devote to HS2 does not represent value.
"We simply do not need to travel at these high speeds in order to achieve the benefits of inter-communication.
"When it comes down to it, HS2 is a disaster for Staffordshire and of no benefit to the country as a whole."
Last month the National Audit Office warned the 2026 target date for opening phase one between London and the West Midlands is at risk.
Rail bosses insist the project is on track to be completed on time.