A project to build a racetrack at Ebbw Vale is "an outrage" and people are being "sold a pipedream', a Conservative MP has warned.
Welsh ministers are considering plans for the £425m Circuit of Wales before deciding whether to back the scheme.
But Monmouth MP David Davies said it was "time to pull the plug".
Lawyers for the project have accused the MP of campaigning to undermine what was potentially one of Wales' most significant regeneration projects.
Welsh Government Economy Secretary Ken Skates has promised "rigorous value for money testing" on the proposals.
Ministers have told developers to find at least half the cash from private sources.
Speaking during the annual Commons Welsh Affairs debate marking St David's Day, Mr Davies said: "It is time to pull the plug on this.
"If the Welsh Government wants to put £200m of our money at risk, there are better ways of doing it, and better people to be doing it with.
"Politicians who support it are being taken out to lunch and those who are asking difficult questions are being threatened with legal advice by an expensive group of city lawyers, £9m worth of taxpayers money is being wasted."
Mr Davies said that he was intrigued as to why the Circuit of Wales project keeps "increasing in costs".
He told MPs he had obtained a copy of a quote - seen by BBC Wales - from the Spanish company FCC that has the contract to build the track.
It is not dated, but prices the project at almost £180m.
Mr Davies said that "even with a few hotels chucked in that takes a bit of explaining".
He said that he had passed on his information to the Wales Audit Office.
In February, the developers said they looked forward to beginning construction by the spring of this year.
They have previously claimed the scheme could eventually result in 6,000 jobs, attract 750,000 visitors a year and inject an estimated £50m into the Welsh economy each year.
Circuit of Wales lawyers said they would study Mr Davies's speech carefully when it is published in the parliamentary record Hansard and give a detailed response then.
They said: "Mr Davies' comments in the House of Commons today are just the latest example of his continued attempts to misrepresent The Circuit of Wales and its developers, based on misinformation and a misunderstanding of the financial structure of the development, despite having been provided detailed information about the project."
The lawyers accused Mr Davies of conducting a "sustained campaign to undermine the efforts made by the Welsh Government to progress The Circuit of Wales, which has the potential to be one of the most significant regeneration projects that Wales has ever seen".
The Circuit of Wales said it will lodge a complaint with the Parliamentary Standards Commissioner about Mr Davies' conduct, on Friday.